Gas laser apparatus

ABSTRACT

A gas laser apparatus may include: a laser chamber connected through a first control valve to a first laser gas supply source that supplies a first laser gas containing a halogen gas and connected through a second control valve to a second laser gas supply source that supplies a second laser gas having a lower halogen gas concentration than the first laser gas; a purification column that removes at least a part of the halogen gas and a halogen compound from at least a part of a gas exhausted from the laser chamber; a booster pump, connected through a third control valve to the laser chamber, which raises a pressure of a gas having passed through the purification column to a gas pressure that is higher than an operating gas pressure of the laser chamber; and a controller that calculates, on a basis of a first amount of a gas supplied from the booster pump through the third control valve to the laser chamber, a second amount of the first laser gas that is to be supplied to the laser chamber and controls the first control valve on a basis of a result of the calculation of the second amount.

TECHNICAL FIELD

The present disclosure relates to a gas laser apparatus.

BACKGROUND ART

In recent years, along with the miniaturization and integration ofsemiconductor integrated circuits, a semiconductor exposure device(hereinafter referred to as “exposure device”) has been required to havehigher resolution. For this reason, shortening of the wavelength oflight that is emitted from an exposure light source has been underdevelopment. Generally, as an exposure light source, a gas laserapparatus is used instead of a conventional mercury lamp. For example,as a gas laser apparatus for exposure, a KrF excimer laser apparatusconfigured to output ultraviolet laser light with a wavelength of 248 nmas well as an ArF excimer laser apparatus configured to outputultraviolet laser light with a wavelength of 193 nm may be used.

As next-generation exposure technology, immersion exposure has been putto practical use. In immersion exposure, a gap between an exposure lensin an exposure device and a wafer is filled with fluid. Since therefractive index between the exposure lens and the wafer changes, anapparent wavelength of the exposure light source is shortened. In a casewhere immersion exposure is performed using an ArF excimer laserapparatus as an exposure light source, a wafer is irradiated withultraviolet light whose wavelength in water is 134 nm. This techniquemay be referred to as “ArF immersion exposure (or ArF immersionlithography)”.

Natural oscillation wavelengths of KrF and ArF excimer laser apparatusesare as wide as approximately 350 to 400 pm. Therefore, the constitutionof a projector lens by a material that transmits ultraviolet rays suchas KrF or ArF laser light may cause chromatic aberration, thus loweringresolution. Therefore, a spectrum line width of laser light that isoutputted from a gas laser apparatus needs to be narrowed to the extentthat chromatic aberration can be ignored. In order to narrow a spectrumline width, a line narrow module (LNM) having a line narrowing element(an etalon, a grating, or the like) may be provided in a laser resonatorof a gas laser apparatus. In the following, a laser apparatus whosespectrum line width is narrowed may be referred to as a “line narrowedlaser apparatus”.

CITATION LIST

Patent Document

Patent Document 1: Japanese Patent No. 4891969

Patent Document 2: United States Patent Application Publication No.2010/0086459

SUMMARY

A gas laser apparatus according to an aspect of the present disclosuremay include: a laser chamber connected through a first control valve toa first laser gas supply source that supplies a first laser gascontaining a halogen gas and connected through a second control valve toa second laser gas supply source that supplies a second laser gas havinga lower halogen gas concentration than the first laser gas; apurification column that removes at least a part of the halogen gas anda halogen compound from at least a part of a gas exhausted from thelaser chamber; a booster pump, connected through a third control valveto the laser chamber, which raises a pressure of a gas having passedthrough the purification column to a gas pressure that is higher than anoperating gas pressure of the laser chamber; and a controller thatcalculates, on a basis of a first amount of a gas supplied from thebooster pump through the third control valve to the laser chamber, asecond amount of the first laser gas that is to be supplied to the laserchamber and controls the first control valve on a basis of a result ofthe calculation of the second amount.

A gas laser apparatus according to another aspect of the presentdisclosure may include: a laser chamber connected through a firstcontrol valve to a first laser gas supply source that supplies a firstlaser gas containing a halogen gas and connected through a secondcontrol valve to a second laser gas supply source that supplies a secondlaser gas having a lower halogen gas concentration than the first lasergas; a purification column that removes at least a part of the halogengas and a halogen compound from at least a part of a gas exhausted fromthe laser chamber; a booster pump, connected through a third controlvalve to the laser chamber, which raises a pressure of a gas havingpassed through the purification column to a gas pressure that is higherthan an operating gas pressure of the laser chamber; a first tankdisposed between the purification column and the booster pump; a firstpressure sensor that measures a first pressure inside the first tank; asecond tank disposed between the booster pump and the third controlvalve; a second pressure sensor that measures a second pressure insidethe second tank; and a controller that controls the booster pump on abasis of the first pressure and controls the third control valve on abasis of the second pressure.

A gas laser apparatus according to another aspect of the presentdisclosure may include: a laser chamber connected through a firstcontrol valve to a first laser gas supply source that supplies a firstlaser gas containing a halogen gas and connected through a secondcontrol valve to a second laser gas supply source that supplies a secondlaser gas having a lower halogen gas concentration than the first lasergas; a fourth control valve disposed between the second laser gas supplysource and the second control valve; a purification column that removesat least a part of the halogen gas and a halogen compound from at leasta part of a gas exhausted from the laser chamber; a booster pump,connected through a third control valve to a pipe between the fourthcontrol valve and the second control valve, which raises a pressure of agas having passed through the purification column to a gas pressure thatis higher than an operating gas pressure of the laser chamber; and acontroller that selectively executes a first control mode in which thethird control valve is closed and the fourth control valve is opened anda second control mode in which the fourth control valve is closed andthe third control valve is opened.

A gas laser apparatus according to still another aspect of the presentdisclosure may include: a first laser chamber connected through a firstcontrol valve to a first laser gas supply source that supplies a firstlaser gas containing a halogen gas and connected through a secondcontrol valve to a second laser gas supply source that supplies a secondlaser gas having a lower halogen gas concentration than the first lasergas; a second laser chamber connected through a sixth control valve tothe first laser gas supply source and connected through a seventhcontrol valve to the second laser gas supply source; a common pipeconnected to the second laser gas supply source and divided into a firstbranch pipe in which the second control valve is disposed and a secondbranch pipe in which the seventh control valve is disposed; a fourthcontrol valve disposed in the common pipe; a purification column thatremoves at least a part of the halogen gas and a halogen compound fromat least a part of a gas exhausted from the first laser chamber and atleast a part of a gas exhausted from the second laser chamber; and abooster pump, connected through the third control valve to the commonpipe between the fourth control valve and a place where the common pipeis divided into the first and second branch pipes, which raises apressure of a gas having passed through the purification column to a gaspressure that is higher than an operating gas pressure of the firstlaser chamber and an operating gas pressure of the second laser chamber.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiments of the present disclosure will be describedhereinafter with reference to the appended drawings.

In the drawings, a dashed arrow means at least one of an input and anoutput of a signal. In the drawings, a solid arrow means the movement ofmatter or the travel of light.

FIG. 1 is a diagram illustrating an example of a configuration of anexcimer laser apparatus.

FIG. 2 is a diagram illustrating an example of operation of a gascontrol unit of the excimer laser apparatus.

FIG. 3 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to a firstembodiment of the present disclosure.

FIG. 4 is a diagram illustrating an example of operation of a gaspurification control unit of the laser apparatus including the gaspurification system according to the first embodiment of the presentdisclosure.

FIG. 5 is a diagram illustrating an example of operation of a gascontrol unit of the laser apparatus including the gas purificationsystem according to the first embodiment of the present disclosure.

FIG. 6 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to asecond embodiment of the present disclosure.

FIG. 7 is a diagram illustrating an example of operation of a gaspurification control unit of the laser apparatus including the gaspurification system according to the second embodiment of the presentdisclosure.

FIG. 8 is a diagram illustrating an example of operation of a gascontrol unit of the laser apparatus including the gas purificationsystem according to the second embodiment of the present disclosure.

FIG. 9 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to a thirdembodiment of the present disclosure.

FIG. 10 is a diagram illustrating an example of operation of a gaspurification control unit of the laser apparatus including the gaspurification system according to the third embodiment of the presentdisclosure.

FIG. 11 is a diagram illustrating an example of operation of a gascontrol unit of the laser apparatus including the gas purificationsystem according to the third embodiment of the present disclosure.

FIG. 12 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to afourth embodiment of the present disclosure.

FIG. 13 is a diagram illustrating an example of operation of a gaspurification control unit of the laser apparatus including the gaspurification system according to the fourth embodiment of the presentdisclosure.

FIG. 14 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to a fifthembodiment of the present disclosure.

FIG. 15 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to a sixthembodiment of the present disclosure.

FIG. 16A is a diagram for explaining a principle of estimation of axenon concentration on the basis of changes in energy E of pulse lightduring burst operation.

FIG. 16B is a diagram for explaining the principle of estimation of axenon concentration on the basis of changes in energy E of pulse lightduring burst operation.

FIG. 16C is a diagram for explaining the principle of estimation of axenon concentration on the basis of changes in energy E of pulse lightduring burst operation.

FIG. 16D is a diagram for explaining the principle of estimation of axenon concentration on the basis of changes in energy E of pulse lightduring burst operation.

FIG. 17A is a diagram for explaining a principle of estimation of axenon concentration on the basis of changes in charging voltage V due toa charger during burst operation.

FIG. 17B is a diagram for explaining the principle of estimation of axenon concentration on the basis of changes in charging voltage V due toa charger during burst operation.

FIG. 17C is a diagram for explaining the principle of estimation of axenon concentration on the basis of changes in charging voltage V due toa charger during burst operation.

FIG. 17D is a diagram for explaining the principle of estimation of axenon concentration on the basis of changes in charging voltage V due toa charger during burst operation.

FIG. 18 is a diagram illustrating an example of operation of a lasercontrol unit of the laser apparatus including the gas purificationsystem according to the sixth embodiment of the present disclosure.

FIG. 19 is a diagram illustrating an example of operation of a gascontrol unit of the laser apparatus including the gas purificationsystem according to the sixth embodiment of the present disclosure.

FIG. 20 is a diagram illustrating an example of operation in which thelaser control unit of the laser apparatus including the gas purificationsystem according to the sixth embodiment of the present disclosureestimates a xenon concentration Cxe.

FIG. 21 is a diagram illustrating an example of operation in which thelaser control unit of the laser apparatus including the gas purificationsystem according to the sixth embodiment of the present disclosureestimates the xenon concentration Cxe.

FIG. 22 is a diagram illustrating an example of a controller accordingto an embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Details

1. Outline 2. Excimer Laser Apparatus 3. Laser Apparatuses Including GasPurification Systems According to Embodiments of Present Disclosure

3.1 Laser Apparatus Including Gas Purification System According to FirstEmbodiment of Present Disclosure

3.2 Laser Apparatus Including Gas Purification System According toSecond Embodiment of Present Disclosure

3.3 Laser Apparatus Including Gas Purification System According to ThirdEmbodiment of Present Disclosure

3.4 Laser Apparatus Including Gas Purification System According toFourth Embodiment of Present Disclosure

3.5 Laser Apparatus Including Gas Purification System According to FifthEmbodiment of Present Disclosure

3.6 Laser Apparatus Including Gas Purification System According to SixthEmbodiment of Present Disclosure

4. Controller According to Embodiment of Present Disclosure

Embodiments of the present disclosure will be described in detailhereinafter with reference to the drawings. The embodiments describedhereinafter indicate several examples of the present disclosure, and arenot intended to limit the content of the present disclosure.Furthermore, not all of the configurations and operations described inthe embodiments are required configurations and operations in thepresent disclosure. Note that identical constituent elements will begiven identical reference numerals, and redundant descriptions thereofwill be omitted.

1. Outline

An embodiment of the present disclosure may relate to a gas purificationsystem. An embodiment of the present disclosure may relate to a laserapparatus. An embodiment of the present disclosure may relate to a laserapparatus including a gas purification system.

A laser apparatus according to an embodiment of the present disclosuremay be a discharge excitation gas laser apparatus. The dischargeexcitation gas laser apparatus may be an apparatus configured for laseroscillation such that a laser gas that is supplied to a chamber isdischarged and excited by applying a predetermined voltage to a pair ofelectrodes disposed in the chamber. The discharge excitation gas laserapparatus may be an excimer laser apparatus. A laser apparatus accordingto an embodiment of the present disclosure may be a laser apparatus foruse in a semiconductor exposure device.

The discharge excitation gas laser apparatus for use in a semiconductorexposure device may be an apparatus configured to output pulse laserlight having a desired energy with longer-term stability. Long-termlaser oscillation in the discharge excitation gas laser apparatus foruse in a semiconductor exposure device may generate impurities in thegas supplied to the chamber of the laser apparatus. The impuritiesgenerated in the gas may absorb pulse laser light or worsen thecondition of discharge of the gas. The impurities generated in the gasmay make it difficult or impossible to output pulse laser light havingthe desired energy.

In order to output pulse laser light having the desired energy, at leasta part of the gas containing the impurities may be replaced with a newgas containing few impurities. In a case where at least a part of thegas containing the impurities is replaced with a new gas containing fewimpurities, there may be an increase in the amount of consumption of agas that is supplied to the chamber of the laser apparatus.

A gas laser apparatus according to an embodiment of the presentdisclosure may include: a laser chamber connected through a firstcontrol valve to a first laser gas supply source that supplies a firstlaser gas containing a halogen gas and connected through a secondcontrol valve to a second laser gas supply source that supplies a secondlaser gas having a lower halogen gas concentration than the first lasergas; a purification column that removes at least a part of the halogengas and a halogen compound from at least a part of a gas exhausted fromthe laser chamber; a booster pump, connected through a third controlvalve to the laser chamber, which raises a pressure of a gas havingpassed through the purification column to a gas pressure that is higherthan an operating gas pressure of the laser chamber; and a controllerthat calculates, on a basis of a first amount of a gas supplied from thebooster pump through the third control valve to the laser chamber, asecond amount of the first laser gas that is to be supplied to the laserchamber and controls the first control valve on a basis of a result ofthe calculation of the second amount.

A gas laser apparatus according to an embodiment of the presentdisclosure may include: a laser chamber connected through a firstcontrol valve to a first laser gas supply source that supplies a firstlaser gas containing a halogen gas and connected through a secondcontrol valve to a second laser gas supply source that supplies a secondlaser gas having a lower halogen gas concentration than the first lasergas; a fourth control valve disposed between the second laser gas supplysource and the second control valve; a purification column that removesat least a part of the halogen gas and a halogen compound from at leasta part of a gas exhausted from the laser chamber; a booster pump,connected through a third control valve to a pipe between the fourthcontrol valve and the second control valve, which raises a pressure of agas having passed through the purification column to a gas pressure thatis higher than an operating gas pressure of the laser chamber; and acontroller that selectively executes a first control mode in which thethird control valve is closed and the fourth control valve is opened anda second control mode in which the fourth control valve is closed andthe third control valve is opened.

A gas laser apparatus according to an embodiment of the presentdisclosure may include: a first laser chamber connected through a firstcontrol valve to a first laser gas supply source that supplies a firstlaser gas containing a halogen gas and connected through a secondcontrol valve to a second laser gas supply source that supplies a secondlaser gas having a lower halogen gas concentration than the first lasergas; a second laser chamber connected through a sixth control valve tothe first laser gas supply source and connected through a seventhcontrol valve to the second laser gas supply source; a common pipeconnected to the second laser gas supply source and divided into a firstbranch pipe in which the second control valve is disposed and a secondbranch pipe in which the seventh control valve is disposed; a fourthcontrol valve disposed in the common pipe; a purification column thatremoves at least a part of the halogen gas and a halogen compound fromat least a part of a gas exhausted from the first laser chamber and atleast a part of a gas exhausted from the second laser chamber; and abooster pump, connected through the third control valve to the commonpipe between the fourth control valve and a place where the common pipeis divided into the first and second branch pipes, which raises apressure of a gas having passed through the purification column to a gaspressure that is higher than an operating gas pressure of the firstlaser chamber and an operating gas pressure of the second laser chamber.

An embodiment of the present disclosure makes it possible to provide agas purification system or a laser apparatus capable of replacing atleast a part of a gas containing impurities with a purified gas. Anembodiment of the present disclosure makes it possible to provide a gaspurification system or a laser apparatus capable of reducing an amountof consumption of a gas.

2. Excimer Laser Apparatus

FIG. 1 is a diagram illustrating an example of a configuration of anexcimer laser apparatus.

An excimer laser apparatus 1000 is a discharge excitation gas laserapparatus. The excimer laser apparatus 1000 may be used together with anexposure device 2000. Laser light emitted from the excimer laserapparatus 1000 may enter the exposure device 2000. The exposure device2000 may include an exposure device controller 2100. The exposure devicecontroller 2100 may be configured to control the semiconductor exposuredevice 2000. The exposure device controller 2100 may be configured tosend a signal to a laser control unit 100 of the laser apparatus 1000.

The excimer laser apparatus 1000 may include the laser control unit 100,a laser oscillation system 200, and a gas control system 300. The lasercontrol unit 100 may be configured to control the laser oscillationsystem 200 and the gas control system 300. The laser control unit 100may be configured to receive signals from a power monitor 220 andchamber pressure sensor 215 of the laser oscillation system 200 and sendsignals to a charger 230 and a switch 214 of a pulse power module (PPM)213. The laser control unit 100 may be configured to receive an emissiontrigger Tr from the exposure device controller 2100.

The laser oscillation system 200 may include a chamber 210, a laserresonator, a power monitor 220, and the charger 230.

The chamber 210 may be configured to generate light by discharging andexciting a gas supplied to the chamber 210 and emitting the light thusgenerated. The chamber 210 may be disposed on an optical path of thelaser resonator. The chamber 210 may include a pair of dischargeelectrodes 211 a and 211 b, two windows 212 a and 212 b, the pulse powermodule 213, and the chamber pressure sensor 215. The pair of dischargeelectrodes 211 a and 211 b may be configured to apply a voltage to a gassupplied into the chamber 210. The two windows 212 a and 212 b may beconfigured to cause the light generated in the chamber 210 to betransmitted out of the chamber 210. The pulse power module 213 may beconfigured to apply a pulse voltage between the pair of dischargeelectrodes 211 a and 211 b. The pulse power module 213 may include theswitch 214. The pulse power module 213 may be configured to apply apulse voltage between the pair of discharge electrodes 211 a and 211 bby switching on and off the switch 214. The switch 214 may receive anemission trigger Tr from the laser control unit 100. The chamberpressure sensor 215 may be configured to measure a pressure (totalpressure) of the gas supplied into the chamber 210. The chamber pressuresensor 215 may be configured to send a signal representing the pressurethus measured to the laser control unit 100 and a gas control unit 310of the gas control system 300.

The laser resonator may be configured to obtain laser light from thelight generated and emitted from the chamber 210. The laser resonatormay include an output coupling (OC) mirror 240 and a line narrow module(LNM) 250. The output coupling mirror 240 may be a partial reflectionmirror configured to transmit a part of the light emitted from thechamber 210 and reflect a part of the light emitted from the chamber210. The line narrow module 250 may be configured to narrow the range ofwavelengths of the light emitted from the chamber 210. The line narrowmodule 250 may include a prism 251 and a grating 252. The prism 251 maybe configured to enlarge the beam diameter of the light emitted from thechamber 210. The prism 251 may be configured to change the angle ofincidence of the light entering the grating 252. The grating 252 may beconfigured to diffract the light emitted from the chamber 210 and selecta wavelength of the light emitted from the chamber 210. Mounting of thegrating 252 may be Littrow mounting, in which the angle of incidence ofthe light entering the grating 252 and the angle of diffraction of thelight diffracted by the grating 252 are completely or substantiallyequal.

The power monitor 220 may be configured to detect pulse energy of laserlight outputted from the output coupling mirror 240. The power monitor220 may include a beam splitter 221, a collector lens 222, and anoptical sensor 223. The beam splitter 221 of the power monitor 220 maybe disposed on the optical path of light from the laser resonator. Thebeam splitter 221 may be configured to transmit a part of the laserlight outputted from the output coupling mirror 240 and reflect a partof the laser light outputted from the output coupling mirror 240. Thecollector lens 222 and optical sensor 223 of the power monitor 220 maybe disposed on an optical path of the laser light reflected by the beamsplitter 221. The collector lens 222 may be configured to focus thelaser light reflected by the beam splitter 221 onto the optical sensor223. The optical sensor 223 may be configured to convert pulse energy ofthe laser light focused by the collector lens 222 into an electricalsignal and send the electrical signal to the laser control unit 100.

The charger 230 may be configured to charge the pulse power module 213.The charger 230 may receive a signal from the laser control unit 100 andbe controlled by the laser control unit 100.

The gas control system 300 may include the gas control unit 310, a gassupply device 320, and an exhaust device 330. The gas control unit 310may be controlled by the laser control unit 100. The gas control unit310 may be configured to send a signal to the laser control unit 100.The gas control unit 310 may receive a signal from the chamber pressuresensor 215 of the laser oscillation system 200. The gas control unit 310may be configured to control the gas supply device 320 and the exhaustdevice 330. The gas control unit 310 may be configured to control valvesF2-V1 and B-V1 of the gas supply device 320 and a valve Ex-V and anexhaust pump 332 of the exhaust device 330.

The gas supply device 320 may include a pipe connected to afluorine-containing gas supply source 3100 and to the chamber 210 of thelaser oscillation system 200. The gas supply device 320 may include thevalve F2-V1 provided in the pipe connected to the fluorine-containinggas supply source 3100 and to the chamber 210 of the laser oscillationsystem 200. The supply of a fluorine-containing gas from thefluorine-containing gas supply source 3100 to the chamber 210 of thelaser oscillation system 200 may be controlled by the valve F2-V1. Thevalve F2-V1 may be controlled by the gas control unit 310.

The gas supply device 320 may include a pipe connected to a buffer gassupply source 3200 and to the chamber 210 of the laser oscillationsystem 200. The gas supply device 320 may include the valve B-V1provided in the pipe connected to the buffer gas supply source 3200 andto the chamber 210 of the laser oscillation system 200. The supply of abuffer gas from the buffer gas supply source 3200 to the chamber 210 ofthe laser oscillation system 200 may be controlled by the valve B-V1.The valve B-V1 may be controlled by the gas control unit 310.

The exhaust device 330 may include a pipe connected to the chamber 210of the laser oscillator system 200 and to the outside. The exhaustdevice 330 may include the valve Ex-V provided in the pipe connected tothe chamber 210 of the laser oscillator system 200 and to the outside.The exhaust of a gas from the chamber 210 of the laser oscillator system200 to the outside may be controlled by the valve Ex-V. The valve Ex-Vmay be controlled by the gas control unit 310. The exhaust device 330may include a fluorine trap 331 and the exhaust pump 332. The fluorinetrap 331 and the exhaust pump 332 may be provided in the pipe connectedto the chamber 210 of the laser oscillator system 200 and to theoutside. The fluorine trap 331 may be configured to trap fluorinecontained in a gas to be exhausted from the chamber 210 of the laseroscillator system 200 to the outside. The exhaust pump 332 may beconfigured to exhaust the gas from the chamber 210 of the laseroscillator system 200 to the outside. Operation of the exhaust pump 332may be controlled by the gas control unit 310.

The fluorine-containing gas supply source 3100 may be a gas cylinderincluding a regulator configured to supply a fluorine-containing gascontaining a fluorine gas that is a halogen gas. The fluorine-containinggas may be a mixed gas of fluorine and rare gasses, such as a mixed gasof fluorine, argon, and neon or a mixed gas of fluorine, krypton, andneon.

The buffer gas supply source 3200 may be a gas cylinder including aregulator configured to supply a buffer gas (a fluorine-free gas). Thebuffer gas may be a mixed gas of rare gasses, such as a mixed gas ofargon and neon or a mixed gas of krypton and neon.

The following describes a method for controlling energy of laser lightin the excimer laser apparatus 1000.

First, upon receiving a target pulse energy Et from the exposure devicecontroller 2100, the laser control unit 100 may send, to the charger230, a signal representing a predetermined charging voltage Vhv forachieving the target pulse energy Et.

Next, upon receiving an emission trigger Tr from the exposure devicecontroller 2100, the laser control unit 100 may apply a voltage betweenthe pair of discharge electrodes 211 a and 211 b by switching on theswitch 214 of the pulse power module 213. Light may be generated in thechamber 210 by discharging and exciting a gas supplied between the pairof discharge electrodes 211 a and 211 b. The light generated in thechamber 210 may be outputted as laser light by the laser resonator. Thelaser light outputted from the laser resonator may be narrowed by thegrating 252 of the laser resonator. The laser light thus narrowed may beoutputted from the output coupling mirror 240. The laser light outputtedfrom the output coupling mirror 240 may enter the power monitor 220.Pulse energy Er of the laser light may be measured by the power monitor220. The pulse energy Er measured by the power monitor 220 may be sentto the laser control unit 100. A part of the laser light outputted fromthe output coupling mirror 240 may enter the exposure device 2000.

Next, on the basis of a difference ΔE between the target pulse energy Etand the pulse energy Er thus measured, the laser control unit 100 mayperform feedback control of the charging voltage Vhv to be sent to thecharger 230.

In this manner, the charging voltage Vhv to be sent to the charger 230may be controlled so that the pulse energy Er thus measured may becomeequal to the target pulse energy Et. The laser apparatus 1000 mayoutput, in synchronization with an emission trigger Tr, pulse laserlight having a predetermined pulse energy.

The following describes an operation of complete gas replacement in theexcimer laser apparatus 1000.

First, the laser control unit 100 may send, to the gas control unit 310of the gas control system 300, a signal for starting complete gasreplacement.

Next, the gas control unit 310 may bring the exhaust pump 332 of theexhaust device 330 into operation.

Next, the gas control unit 310 may open the valve Ex-V to exhaust thegas in the chamber 210 until a pressure P1 measured by the chamberpressure sensor 215 becomes a pressure that is close to a vacuum.

Next, the gas control unit 310 may close the valve Ex-V and stop theexhaust pump 332.

Next, the gas control unit 310 may control the opening and closing ofthe valves F2-V1 and B-V1 so that the pressure P1 measured by thechamber pressure sensor 215 may become equal to a predetermined pressureand the composition of a gas that is supplied to the chamber 210 becomesa predetermined composition.

In this manner, complete gas replacement in the excimer laser apparatus1000 may be performed.

The following describes an operation of partial gas replacement in theexcimer laser apparatus 1000.

Continuation of laser oscillation in the excimer laser apparatus 1000may generate impurities, i.e., fluorine compounds, in the gas containedin the chamber 210. Examples of the impurities, i.e., fluorinecompounds, may include hydrogen fluoride (HF), carbon tetrafluoride(CF₄), silicon tetrafluoride (SiF₄), nitrogen trifluoride (NF₃),hexafluoroethane (C₂F₆), and the like. The impurities generated in thegas contained in the chamber 210 may absorb pulse laser light or worsenthe condition of discharge of the gas. The impurities generated in thegas contained in the chamber 210 may drop the energy of the pulse laserlight or degrade the stability of the energy of the pulse laser light.In order to suppress an increase in concentration of the impurities inthe gas contained in the chamber 210, it is possible to supply thechamber 210 with a predetermined amount of a new gas containing fewimpurities and exhaust the gas in the chamber 210 by the same amount asthe amount of the new gas. In this manner, partial gas replacement inthe excimer laser apparatus 1000 may be performed.

FIG. 2 is a diagram illustrating an example of operation of the gascontrol unit of the excimer laser apparatus.

In step S101, the gas control unit 310 may make preparations for partialgas replacement. In preparation for partial gas replacement, the valveF2-V1 and valve B-V1 of the gas supply device 320 and the valve Ex-V ofthe exhaust device 330 may all be closed. In preparation for partial gasreplacement, the exhaust pump 332 of the exhaust device 330 may bebrought into operation.

In step S102, the gas control unit 310 may determine whether it hasreceived, from the laser control unit 100, a signal for starting partialgas replacement. The laser control unit 100 may send the signal forstarting partial gas replacement to the gas control unit 310 inaccordance with a predetermined number of shots of laser oscillation,predetermined time intervals, or the like. In a case where the gascontrol unit 310 has received, from the laser control unit 100, thesignal for starting partial gas replacement, the gas control unit 310may proceed to step S103. In a case where the gas control unit 310 hasnot received, from the laser control unit 100, the signal for startingpartial gas replacement, the gas control unit 310 may repeat step S102.

In step S103, the gas control unit 310 may receive an initial pressureP10 of the gas in the chamber 210 (i.e., a pressure of the gas in thechamber 210 before partial gas replacement) from the chamber pressuresensor 215.

In step S104, the gas control unit 310 may calculate a target value P1 bof the pressure of the gas in the chamber 210 after supplying the buffergas to the chamber 210.

In step S105, the gas control unit 310 may receive the pressure P1 ofthe gas in the chamber 210 from the chamber pressure sensor 215 and maycontrol the valve B-V1 so that the pressure P1 may become closer to thetarget value P1 b. In this manner, the buffer gas may be supplied to thechamber 210.

In step S106, the gas control unit 310 may calculate a target valueΔP1F2 of a rise in pressure in the chamber 210 due to supplying thefluorine-containing gas to the chamber 210. The gas control unit 310 maycalculate the target value ΔP1F2 of the rise in pressure so that theconcentration of a fluorine gas in the gas in the chamber 210 may becomeequal to a predetermined concentration CF2. For example, in a case wherethe fluorine-containing gas is a fluorine gas, the target value ΔP1F2 ofthe rise in pressure may be calculated according to the formulae ΔP1b=P1 b−P10 and ΔP1F2=CF2×ΔP1 b/(1−CF2). In a case where thefluorine-containing gas is a mixed gas, the calculation may be performedfurther in consideration of the mixing ratio of fluorine.

In step S107, the gas control unit 310 may calculate a target value P1F2of the pressure of the gas in the chamber 210 after supplying thefluorine-containing gas to the chamber 210. The target value P1F2 of thepressure may be calculated according to the formula P1F2=P1 b+ΔP1F2.

In step S108, the gas control unit 310 may receive the pressure P1 ofthe gas in the chamber 210 from the chamber pressure sensor 215 and maycontrol the valve F2-V1 so that the pressure P1 may become closer to thetarget value P1F2. In this manner, the fluorine-containing gas may besupplied to the chamber 210.

In step S109, the gas control unit 310 may receive the pressure P1 ofthe gas in the chamber 210 from the chamber pressure sensor 215 and maycontrol the valve Ex-V so that the pressure P1 may become closer to theinitial pressure P10. In this manner, a part of the gas in the chamber210 may be exhausted to the outside.

In step S110, the gas control unit 310 may determine whether it hasreceived, from the laser control unit 100, a signal for stopping partialgas replacement. The laser control unit 100 may send the signal forstopping partial gas replacement to the gas control unit 310 inaccordance with the pressure P1 measured by the chamber pressure sensor215 or the like. In a case where the gas control unit 310 has received,from the laser control unit 100, the signal for stopping partial gasreplacement, the gas control unit 310 may terminate the operation forpartial gas replacement. In a case where the gas control unit 310 hasnot received, from the laser control unit 100, the signal for stoppingpartial gas replacement, the gas control unit 310 may return to stepS102.

An amount Q of a gas that is replaced by a single round of partial gasreplacement may be calculated according to the formula Q=(ΔP1b+ΔP1F2)×V/P, where V is the volume of the chamber 210 and P is 1 atm(1013 hPa).

In this manner, an increase in the concentration of impurities that maybe generated in the gas in the chamber 210 may be suppressed byreplacing the predetermined amount Q of the gas in the chamber 210 withthe predetermined number of shots of laser oscillation or at thepredetermined time intervals.

In a case where a new gas containing few impurities is supplied to thechamber 210 and the gas in the chamber 210 is exhausted by the sameamount as the amount of the new gas in order to suppress an increase inthe concentration of impurities in the gas in the chamber 210, theamount of consumption of gas may increase.

3. Laser Apparatuses Including Gas Purification Systems According toEmbodiments of Present Disclosure

3.1 Laser Apparatus Including Gas Purification System According to FirstEmbodiment of Present Disclosure

FIG. 3 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to a firstembodiment of the present disclosure. The laser apparatus shown in FIG.3 may include the same configuration as the laser apparatus illustratedin FIG. 1. Components of the laser apparatus illustrated in FIG. 3 whichare identical to those of the laser apparatus illustrated in FIG. 1 aregiven the same reference signs, and as such, are omitted from thedescription below.

The excimer laser apparatus 1000 according to the first embodiment ofthe present disclosure may further include a gas purification system400.

The gas purification system 400 may include a gas purification device410 and a gas purification control unit 420. The gas purificationcontrol unit 420 may be configured to receive a signal from the gascontrol unit 310 of the gas control system 300 and send a signal to thegas control unit 310. The gas purification control unit 420 may beconfigured to control the gas purification device 410.

The gas purification device 410 may include a purification column 411, afilter 412, a circulation pump 413, a mass flow controller (MFC) 414, avalve C-V1, a valve C-V2, and a valve C-V3. The gas purification device410 may include a circulation gas pipe connecting the valve C-V1, thepurification column 411, the filter 412, the circulation pump 413, themass flow controller 414, and the valve C-V3. The gas purificationdevice 410 may include a bypass pipe connecting a pipe between the valveC-V1 and the purification column 411 and a pipe between the circulationpump 413 and the mass flow controller 414. The bypass pipe may beprovided with the valve C-V2.

One end of the circulation gas pipe may be connected to a pipe connectedto both the chamber 210 of the laser oscillation system 200 and theexhaust device 330 of the gas control system 300. The other end of thecirculation gas pipe may be connected to a pipe connected to both thechamber 210 of the laser oscillation system 200 and the gas supplydevice 320 of the gas control system 300.

The purification column 411, the circulation pump 413, the mass flowcontroller 414, the valve C-V1, the valve C-V2, and the valve C-V3 maybe configured to receive signals from the gas purification control unit420. The purification column 411, the circulation pump 413, the massflow controller 414, the valve C-V1, the valve C-V2, and the valve C-V3may be configured to be controlled by the gas purification control unit420.

The purification column 411 may include a first treatment tower (notillustrated) and a second treatment tower (not illustrated). The firsttreatment tower may be filled with a treating agent for treating afluorine gas and impurities, i.e., fluorine compounds. The treatingagent for treating the fluorine gas and the impurities, i.e., thefluorine compounds, may be a treating agent containing at least one ofzeolite and calcium oxide. The second treatment tower may be filled witha treating agent for treating at least one of moisture and oxygengenerated by the treatment of the fluorine gas and the impurities, i.e.,the fluorine compounds, by the treating agent filled in the firsttreatment tower. The treating agent for treating at least one ofmoisture and oxygen may be a treating agent containing at least one of anickel (Ni) catalyst, a copper (Cu) catalyst, and a compound thereof.The purification column 411 may include a heating device (and atemperature regulating device) (not illustrated) for causing the firsttreatment tower and the second treatment tower to operate at atemperature that is higher than room temperature.

The filter 412 may be a filter for trapping particles generated by thedischarge of a gas supplied between the pair of discharge electrodes 211a and 211 b in the chamber 210. The filter 412 may be a filter made of amaterial that hardly reacts with fluorine. The material that hardlyreacts with fluorine may be a metal or ceramic material.

The circulation pump 413 may be a pump configured to cause a gas to flowthrough the circulation gas pipe.

The mass flow controller 414 may be a valve configured to control themass flow of the gas flowing through the circulation gas pipe.

The following describes an operation of complete gas replacement in theexcimer laser apparatus 1000 according to the first embodiment of thepresent disclosure.

First, the laser control unit 100 may send a signal for startingcomplete gas replacement to the gas control unit 310 of the gas controlsystem 300.

Next, the gas control unit 310 may bring the exhaust pump 332 of theexhaust device 330 into operation.

Next, the gas control unit 310 and the gas purification control unit 420may open the valve Ex-V, the valve CV-1, the valve C-V2, and the valveC-V3 to exhaust the gas in the chamber 210 and the gas in the pipe ofthe gas purification device 410. The gas control unit 310 and the gaspurification control unit 420 may exhaust the gas in the chamber 210 andthe gas in the pipe of the gas purification device 410 until thepressure P1 measured by the chamber pressure sensor 215 becomes apressure that is close to a vacuum.

Next, the gas control unit 310 may close the valve Ex-V and stop theexhaust pump 332.

Next, the gas control unit 310 may control the opening and closing ofthe valves F2-V1 and B-V1 so that the pressure P1 measured by thechamber pressure sensor 215 may become equal to a predetermined pressureand the composition of a gas that is supplied to the chamber 210 maybecome a predetermined composition.

Next, the gas purification control unit 420 may close the valve C-V1,the valve C-V2, and the valve C-V3.

In this manner, the chamber 210 and the gas purification device 420 maybe filled with a gas. In this manner, complete gas replacement in theexcimer laser apparatus 1000 may be performed.

Furthermore, the gas purification control unit 420 may heat thepurification column 411 (and control the temperature of the purificationcolumn 411).

FIG. 4 is a diagram illustrating an example of operation of the gaspurification control unit of the laser apparatus including the gaspurification system according to the first embodiment of the presentdisclosure.

In step S201, the gas purification control unit 420 may makepreparations for gas purification. In preparation for gas purification,the circulation gas pipe and bypass pipe of the gas purification controlunit 410 may be filled with a gas. In preparation for gas purification,the purification column 411 may be heated. In preparation for gaspurification, the valve C-V1, the valve C-V2, and the valve C-V3 may beclosed.

In step S202, the gas purification control unit 420 may determinewhether it has received, from the laser control unit 100 through the gascontrol unit 310, a signal for starting gas purification. The lasercontrol unit 100 may send the signal for starting gas purification tothe gas purification control unit 420 through the gas control unit 310in accordance with the predetermined number of shots of laseroscillation, the predetermined time intervals, and the like. In a casewhere the gas purification control unit 420 has received, from the lasercontrol unit 100 through the gas control unit 310, the signal forstarting gas purification, the gas purification control unit 420 mayproceed to step S203. In a case where the gas purification control unit420 has not received, from the laser control unit 100 through the gascontrol unit 310, the signal for starting gas purification, the gaspurification control unit 420 may repeat step S202.

In step S203, the gas purification control unit 420 may bring thecirculation pump 413 of the gas purification device 410 into operation.

In step S204, the gas purification control unit 420 may set a flow rateL of a gas that is controlled by the mass flow controller 414 of the gaspurification device 410. The setting of the flow rate L of the gas thatis controlled by the mass flow controller 414 of the gas purificationdevice 410 may be carried out by sending the flow rate L from the gaspurification control unit 420 to the mass flow controller 414.

In step S205, the gas purification control unit 420 may open the valveC-V1 of the gas purification device 410.

In step S206, the gas purification control unit 420 may wait for apredetermined period of time T1. By the gas purification control unit420 waiting for the predetermined period of time T1, the pressure of thegas in the circulation gas pipe of the gas purification device 410 maybe made substantially equal to the pressure of the gas in the chamber210.

In step S207, the gas purification control unit 420 may open the valveC-V2 of the gas purification device 410 and close the valve C-V1.

In step S208, the gas purification control unit 420 may wait for apredetermined period of time T2. By the gas purification control unit420 waiting for the predetermined period of time T2, the gas containedin the gas purification device 410 may be circulated through thecirculation gas pipe and the bypass pipe and more effectively purifiedby the purification column 411 and the filter 412.

In step S209, the gas purification control unit 420 may close the valveC-V2 of the gas purification device 410 and open the valve C-V1 andvalve C-V3 of the gas purification device 410.

In step S210, the gas purification control unit 420 may wait for apredetermined period of time T3. While the gas purification control unit420 is waiting for the predetermined period of time T3, the circulationpump 413 and the mass flow controller 414 may supply the gas purified bythe purification column 411 and the filter 412 to the chamber 210 at theflow rate L through the circulation gas pipe.

In step S211, the gas purification control unit 420 may close the valveC-V1 and valve C-V3 of the gas purification device 410.

In step S212, the gas purification control unit 420 may calculate anamount Qb of the purified gas supplied to the chamber 210. The amount Qbof the purified gas supplied to the chamber 210 may be calculatedaccording to the formula Qb=L×T3. The gas purification control unit 420may send, to the laser control unit 100 through the gas control unit310, the amount Qb of the purified gas supplied to the chamber 210.

In step S213, the gas purification control unit 420 may determinewhether it has received, from the laser control unit 100 through the gascontrol unit 310, a signal for stopping gas purification. The lasercontrol unit 100 may send the signal for stopping gas purification tothe gas purification control unit 420 through the gas control unit 310in accordance with the pressure P1 measured by the chamber pressuresensor 215 and the like. In a case where the gas purification controlunit 420 has received, from the laser control unit 100 through the gascontrol unit 310, the signal for stopping gas purification, the gaspurification control unit 420 may stop the circulation pump 413 of thegas purification device 410 in step S214. Then, the operation of gaspurification may be terminated. In a case where the gas purificationcontrol unit 420 has not received, from the laser control unit 100through the gas control unit 310, the signal for stopping gaspurification, the gas purification control unit 420 may return to stepS205.

FIG. 5 is a diagram illustrating an example of operation of the gascontrol unit of the laser apparatus including the gas purificationsystem according to the first embodiment of the present disclosure.

In step S301, the gas control unit 310 may make preparations for partialgas replacement. In preparation for partial gas replacement, the valveF2-V1 and valve B-V1 of the gas supply device 320 and the valve Ex-V ofthe exhaust device 330 may all be closed. In preparation for partial gasreplacement, the exhaust pump 332 of the exhaust device 330 may bebrought into operation.

In step 302, the gas control unit 310 may determine whether it hasreceived, from the laser control unit 100, data representing the amountQb of the purified gas supplied to the chamber 210. The laser controlunit 100 may send, to the gas control unit 310, the amount Qb of thepurified gas supplied to the chamber 210 thus received from the gaspurification control unit 420. In a case where the gas control unit 310has received, from the laser control unit 100, data representing theamount Qb of the purified gas supplied to the chamber 210, the gascontrol unit 310 may proceed to step S303. In a case where the gascontrol unit 310 has not received, from the laser control unit 100, datarepresenting the amount Qb of the purified gas supplied to the chamber210, the gas control unit 310 may repeat step S302.

In step S303, the gas control unit 310 may read out the amount Qb,received from the laser control unit 100, of the purified gas suppliedto the chamber 210. In a case where the purified gas supplied to thechamber 210 completely or substantially does not contain a fluorine gas,the concentration of fluorine in the gas in the chamber 210 may bereduced. In order to suppress a reduction in the concentration offluorine in the gas in the chamber 210, fluorine-containing gas may besupplied (replenished) from the fluorine-containing gas supply source3100 into the chamber 210, depending on the amount Qb of the purifiedgas supplied to the chamber 210.

In step S304, the gas control unit 310 may receive an initial pressureP10 of the gas in the chamber 210 (i.e., a pressure of the gas in thechamber 210 before partial gas replacement) from the chamber pressuresensor 215.

In step S305, the gas control unit 310 may calculate a target valueΔP1F2 of a rise in pressure in the chamber 210 due to supplying thefluorine-containing gas to the chamber 210. The gas control unit 310 maycalculate the target value ΔP1F2 of the rise in pressure so that theconcentration of a fluorine gas in the gas in the chamber 210 may becomeequal to a predetermined concentration CF2. For example, in a case wherethe fluorine-containing gas is a fluorine gas, the target value ΔP1F2 ofthe rise in pressure may be calculated according to the formulaΔP1F2=CF2×(Qb/V)/(1−CF2), where V is the volume of the chamber 210. In acase where the fluorine-containing gas is a mixed gas, the calculationmay be performed further in consideration of a mixing ratio of fluorine.

In step S306, the gas control unit 310 may calculate a target value P1F2of the pressure of the gas in the chamber 210 after supplying thefluorine-containing gas to the chamber 210. The target value P1F2 of thepressure may be calculated according to the formula P1F2=P10+Qb/V+ΔP1F2.

In step S307, the gas control unit 310 may receive the pressure P1 ofthe gas in the chamber 210 from the chamber pressure sensor 215 and maycontrol the valve F2-V1 so that the pressure P1 may become closer to thetarget value P1F2. In this manner, the fluorine-containing gas may besupplied to the chamber 210.

In step S308, the gas control unit 310 may receive the pressure P1 ofthe gas in the chamber 210 from the chamber pressure sensor 215 and maycontrol the valve Ex-V so that the pressure P1 may become closer to theinitial pressure P10. In this manner, a part of the gas in the chamber210 may be exhausted to the outside.

In step S309, the gas control unit 310 may determine whether it hasreceived, from the laser control unit 100, a signal for stopping partialgas replacement. The laser control unit 100 may send the signal forstopping partial gas replacement to the gas control unit 310 based onthe pressure P1 measured by the chamber pressure sensor 215 and thelike. In a case where the gas control unit 310 has received, from thelaser control unit 100, the signal for stopping partial gas replacement,the gas control unit 310 may terminate the operation for partial gasreplacement. In a case where the gas control unit 310 has not received,from the laser control unit 100, the signal for stopping partial gasreplacement, the gas control unit 310 may return to step S302.

In the excimer laser apparatus 1000 according to the first embodiment ofthe present disclosure, the mass flow controller 414 is used to obtainthe amount of the purified gas that is supplied to the chamber 210.Alternatively, a flowmeter may be provided instead of the mass flowcontroller 414.

In this manner, the laser apparatus 1000 according to the firstembodiment of the present disclosure makes it possible to purify a partof the gas in the chamber 210 and supply the purified gas to the chamber210. In this manner, the laser apparatus 1000 according to the firstembodiment of the present disclosure makes it possible to reduce theamount of a gas that is sent from the buffer gas supply source 3200 tothe chamber 210.

3.2 Laser Apparatus Including Gas Purification System According toSecond Embodiment of Present Disclosure

FIG. 6 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to asecond embodiment of the present disclosure. The laser apparatus shownin FIG. 6 may include the same configuration as the laser apparatusillustrated in FIG. 1. Components of the laser apparatus illustrated inFIG. 6 which are identical to those of the laser apparatus illustratedin FIG. 1 are given the same reference signs, and as such, are omittedfrom the description below. The excimer laser apparatus 1000 accordingto the second embodiment of the present disclosure may further include agas purification system 500.

The gas purification system 500 may include a gas purification device510 and a gas purification control unit 520. The gas purificationcontrol unit 520 may be configured to receive a signal from the gascontrol unit 310 of the gas control system 300 and send a signal to thegas control unit 310. The gas purification control unit 520 may beconfigured to receive a signal from the gas purification device 510 andsend a signal to the gas purification device 510.

The gas purification device 510 may include a purification column 511, afirst filter 512, a first tank 513, a first pressure sensor 514, abooster pump 515, a second filter 516, a second tank 517, a secondpressure sensor 518, a purifier 519, a valve C-V1, and a valve C-V3. Thegas purification device 510 may include a circulation gas pipeconnecting the valve C-V1, the purification column 511, the first filter512, the first tank 513, the booster pump 515, the second filter 516,the second tank 517, the purifier 519, and the valve C-V3.

One end of the circulation gas pipe may be connected to a pipe connectedto both the chamber 210 of the laser oscillation system 200 and theexhaust device 330 of the gas control system 300. The other end of thecirculation gas pipe may be connected to a pipe connected to both thechamber 210 of the laser oscillation system 200 and the gas supplydevice 320 of the gas control system 300.

The purification column 511 and the booster pump 515 may be configuredto receive a signal from the gas purification control unit 520. Thepurification column 511 and the booster pump 515 may be configured to becontrolled by the gas purification control unit 520.

The first pressure sensor 514 and the second pressure sensor 518 may beconfigured to send signals representing measured pressures to the gaspurification control unit 520.

The valve C-V1 and the valve C-V3 may be configured to receive signalsfrom the gas control unit 310 of the gas control system 300. The valveC-V1 and the valve C-V3 may be configured to be controlled by the gascontrol unit 310 of the gas control system 300.

The purification column 511 may include a first treatment tower (notillustrated) and a second treatment tower (not illustrated). The firsttreatment tower may be filled with a treating agent for treating afluorine gas and impurities, i.e., fluorine compounds. The treatingagent for treating the fluorine gas and the impurities, i.e., thefluorine compounds, may be a treating agent containing at least one ofzeolite and calcium oxide. The second treatment tower may be filled witha treating agent for treating at least one of moisture and oxygengenerated by the treatment of the fluorine gas and the impurities, i.e.,the fluorine compounds, by the treating agent filling the firsttreatment tower. The treating agent for treating at least one ofmoisture and oxygen may be a treating agent containing at least one of anickel (Ni) catalyst, a copper (Cu) catalyst, and a compound thereof.The purification column 511 may include a heating device (and atemperature regulating device) (not illustrated) for causing the firsttreatment tower and the second treatment tower to operate at atemperature that is higher than room temperature.

The first filter 512 and the second filter 516 may each be a filter fortrapping particles generated by discharge of a gas supplied between thepair of discharge electrodes 211 a and 211 b in the chamber 210. Thefirst filter 512 and the second filter 516 may each be a filter made ofa material that hardly reacts with fluorine. The material that hardlyreacts with fluorine may be a metal or ceramic material.

The first tank 513 may be a container configured to contain a gaspurified by the purification column 511 and the first filter 512. Thevolume of the first tank 513 may be 5 liters or larger and 15 liters orsmaller.

The first pressure sensor 514 may be configured to measure a pressure ofthe purified gas contained in the first tank 513. The first pressuresensor 514 may be provided in the first tank 513. The first pressuresensor 514 may be configured to send a signal representing the measuredgas pressure to the gas purification control unit 520.

The second tank 517 may be a container configured to contain a purifiedgas that is sent from the first tank 513 by the booster pump 515. Thevolume of the second tank 517 may be 5 liters or larger and 15 liters orsmaller.

The second pressure sensor 518 may be configured to measure a pressureof the purified gas contained in the second tank 517. The secondpressure sensor 518 may be provided in the second tank 517. The secondpressure sensor 518 may be configured to send a signal representing themeasured gas pressure to the gas purification control unit 520.

The booster pump 515 may be a pump configured to cause a gas to flowthrough the circulation gas pipe. The booster pump 515 may be providedbetween the first tank 513 and the second tank 517. The booster pump 515may be configured to send a gas from the first tank 513 to the secondtank 517. The booster pump 515 may receive a signal from the gaspurification control unit 520 and be controlled by the gas purificationcontrol unit 520.

The purifier 519 may be a metal filter including a metal getter servingas a purification agent for a gas contained in the circulation gas pipe.

The following describes an operation of complete gas replacement in theexcimer laser apparatus 1000 according to the second embodiment of thepresent disclosure.

First, the laser control unit 100 may send a signal for startingcomplete gas replacement to the gas control unit 310 of the gas controlsystem 300.

Next, the gas control unit 310 may bring the exhaust pump 332 of theexhaust device 330 into operation.

Next, the gas control unit 310 may open the valve Ex-V, the valve CV-1,and the valve C-V3 to exhaust the gas in the chamber 210 and the gas inthe pipe of the gas purification device 510. The gas control unit 310may exhaust the gas in the chamber 210 and the gas in the pipe of thegas purification device 510 until the pressure P1 measured by thechamber pressure sensor 215 becomes a pressure that is close to avacuum.

Next, the gas control unit 310 may close the valve Ex-V and stop theexhaust pump 332. The gas control unit 310 may close the valve C-V1 andthe valve C-V3.

Next, the gas control unit 310 may control the opening and closing ofthe valves F2-V1 and B-V1 so that the pressure P1 measured by thechamber pressure sensor 215 may become equal to a predetermined pressureand the composition of a gas that is supplied to the chamber 210 maybecome a predetermined composition.

In this manner, the chamber 210 may be filled with a gas. The gaspurification device 520 may be completely or substantially in a vacuumstate. In this manner, complete gas replacement in the excimer laserapparatus 1000 according to the second embodiment of the presentdisclosure may be performed.

Furthermore, the gas purification control unit 520 may heat thepurification column 511 (and control the temperature of the purificationcolumn 511).

FIG. 7 is a diagram illustrating an example of operation of the gaspurification control unit of the laser apparatus including the gaspurification system according to the second embodiment of the presentdisclosure.

In step S401, the gas purification control unit 520 may makepreparations for gas purification. In preparation for gas purification,the circulation gas pipe of the gas purification device 510 may befilled with a gas. In preparation for gas purification, the purificationcolumn 511 may be heated. In preparation for gas purification, the valveC-V1 and the valve C-V3 may be closed.

In step S402, the gas purification control unit 520 may determinewhether it has received, from the laser control unit 100 through the gascontrol unit 310, a signal for starting gas purification. The lasercontrol unit 100 may send the signal for starting gas purification tothe gas purification control unit 520 through the gas control unit 310based on the predetermined number of shots of laser oscillation, thepredetermined time intervals, and the like. In a case where the gaspurification control unit 520 has received, from the laser control unit100 through the gas control unit 310, the signal for starting gaspurification, the gas purification control unit 520 may proceed to stepS403. In a case where the gas purification control unit 520 has notreceived, from the laser control unit 100 through the gas control unit310, the signal for starting gas purification, the gas purificationcontrol unit 520 may repeat step S402.

In step S403, the gas control unit 310 of the gas control system 300 mayas needed control the opening and closing of the valve C-V1 and therebyintroduce the gas in the chamber 210 of the laser oscillation system 200into the gas purification device 510. The gas in the chamber 210 whichis introduced into the gas purification device 510 may be purified bythe purification column 511 and the first filter 512 of the gaspurification device 510. The gas thus purified may be supplied to thefirst tank 513 of the gas purification device 510.

In step S404, the gas purification control unit 520 may control thebooster pump 515 of the gas purification device 510. The gaspurification control unit 520 may receive a pressure P2 of the gas inthe first tank 513 of the gas purification device 510 as measured by thefirst pressure sensor 514 of the gas purification device 510. Thebooster pump 515 may be controlled so that the pressure P2 of the gas inthe first tank 513 of the gas purification device 510 may fall within apredetermined range of pressure. The booster pump 515 may be controlledso that the pressure P2 of the gas in the first tank 513 may satisfyP2min≦P2≦P2max. P2min may be the atmospheric pressure (1013 hPa). P2maxmay be a pressure (e.g., 1300 hPa) that is higher than the atmosphericpressure. The booster pump 515 may be configured to send the gascontained in the first tank 513 to the second tank 517. When thepressure P2 of the gas in the first tank 513 satisfies P2min≦P2, thebooster pump 515 may more efficiently send the gas contained in thefirst tank 513 to the second tank 517. When the pressure P2 of the gasin the first tank 513 satisfies P2≦P2max, the booster pump 515 may moreefficiently send a part of the gas in the chamber 210 to the first tank513 of the gas purification device 510.

In step S405, the gas purification control unit 520 may receive apressure P3 of the gas in the second tank 517 of the gas purificationdevice 510 as measured by the second pressure sensor 518 of the gaspurification device 510.

In step S406, the gas purification control unit 520 may determinewhether the pressure P3 of the gas in the second tank 517 is equal to orhigher than a predetermined pressure P3reg. The predetermined pressureP3reg may be a pressure (e.g., 5000 hPa or higher and 5700 hPa or lower)indicated by a regulator provided in a pipe through which the buffer gasis supplied. In a case where the pressure P3 of the gas in the secondtank 517 is equal to or higher than the predetermined pressure P3reg,the gas purification control unit 520 may proceed to step S407. In acase where the pressure P3 of the gas in the second tank 517 is equal toor higher than the predetermined pressure P3reg, the gas in the secondtank 517 may be more efficiently sent to the chamber 210. In a casewhere the pressure P3 of the gas in the second tank 517 is not equal toor higher than the predetermined pressure P3reg, the gas purificationcontrol unit 520 may return to step S403.

In step S407, the gas purification control unit 520 may send, to the gascontrol unit 310, a signal permitting the supply of purified gas to thechamber 210.

In step S408, the gas control unit 310 of the gas control system 300 mayas needed control the opening and closing of the valve C-V3 and therebyintroduce the purified gas in the gas purification device 510 into thechamber 210 of the laser oscillation system 200.

In step S409, the gas purification control unit 520 may determinewhether it has received, from the laser control unit 100 through the gascontrol unit 310, a signal for stopping gas purification. The lasercontrol unit 100 may send the signal for stopping gas purification tothe gas purification control unit 520 through the gas control unit 310based on the pressure P1 measured by the chamber pressure sensor 215 andthe like. In a case where the gas purification control unit 520 hasreceived, from the laser control unit 100 through the gas control unit310, the signal for stopping gas purification, the gas purificationcontrol unit 520 may terminate the operation of gas purification. In acase where the gas purification control unit 520 has not received, fromthe laser control unit 100 through the gas control unit 310, the signalfor stopping gas purification, the gas purification control unit 520 mayreturn to step S403.

FIG. 8 is a diagram illustrating an example of operation of the gascontrol unit of the laser apparatus including the gas purificationsystem according to the second embodiment of the present disclosure.

In step S501, the gas control unit 310 may make preparations for partialgas replacement. In preparation for partial gas replacement, the valveF2-V1 and valve B-V1 of the gas supply device 320 and the valve Ex-V ofthe exhaust device 330 may all be closed. In preparation for partial gasreplacement, the valve C-V1 may as needed be opened to increase thepressure P3 of the gas in the second tank 513.

In step S502, the gas control unit 310 may determine whether it hasreceived, from the laser control unit 100, a signal for starting partialgas replacement and whether it has received, from the gas purificationcontrol unit 520, a signal permitting the supply of the purified gas tothe chamber 210. The laser control unit 100 may send the signal forstarting partial gas replacement to the gas control unit 310 based on apredetermined number of shots of laser oscillation, predetermined timeintervals, and the like. The gas purification control unit 520 may sendthe signal permitting the supply of the purified gas to the chamber 210to the gas control unit 310 based on the value of the pressure P3measured by the second pressure sensor 518. In a case where the gascontrol unit 310 has received both the signal for starting partial gasreplacement from the laser control unit 100 and the signal permittingthe supply of the purified gas to the chamber 210 from the gaspurification control unit 520, the gas control unit 310 may proceed tostep S503. In a case where the gas control unit 310 has not received atleast either the signal for starting partial gas replacement from thelaser control unit 100 or the signal permitting the supply of thepurified gas to the chamber 210 from the gas purification control unit520, the gas control unit 310 may repeat step S502.

In step S503, the gas control unit 310 may receive an initial pressureP10 of the gas in the chamber 210 (i.e., a pressure of the gas in thechamber 210 before partial gas replacement) from the chamber pressuresensor 215.

In step S504, the gas control unit 310 may calculate a target value P1 bof the pressure of the gas in the chamber 210 after supplying thepurified gas to the chamber 210.

In step S505, the gas control unit 310 may receive the pressure P1 ofthe gas in the chamber 210 from the chamber pressure sensor 215 and maycontrol the valve C-V3 so that the pressure P1 may become closer to thetarget value P1 b. In this manner, the purified gas may be supplied fromthe gas purification device 510 to the chamber 210.

In step S506, the gas control unit 310 may calculate a target valueΔP1F2 of a rise in pressure in the chamber 210 due to supplying thefluorine-containing gas to the chamber 210. The gas control unit 310 maycalculate the target value ΔP1F2 of the rise in pressure so that theconcentration of a fluorine gas in the gas in the chamber 210 may becomeequal to a predetermined concentration CF2. For example, in a case wherethe fluorine-containing gas is a fluorine gas, the target value ΔP1F2 ofthe rise in pressure may be calculated according to the formulae ΔP1b=P1 b−P10 and ΔP1F2=CF2×ΔP1 b/(1−CF2). In a case where thefluorine-containing gas is a mixed gas, the calculation may be performedfurther in consideration of a mixing ratio of fluorine.

In step S507, the gas control unit 310 may calculate a target value P1F2of the pressure of the gas in the chamber 210 after supplying thefluorine-containing gas to the chamber 210. The target value P1F2 of thepressure may be calculated according to the formula P1F2=P1 b+ΔP1F2.

In step S508, the gas control unit 310 may receive the pressure P1 ofthe gas in the chamber 210 from the chamber pressure sensor 215 and maycontrol the valve F2-V1 so that the pressure P1 may become closer to thetarget value P1F2. In this manner, the fluorine-containing gas may besupplied to the chamber 210.

In step S509, the gas control unit 310 may receive the pressure P1 ofthe gas in the chamber 210 from the chamber pressure sensor 215 and maycontrol the valve C-V1 so that the pressure P1 may become closer to theinitial pressure P10. In this manner, a part of the gas in the chamber210 may be introduced into the gas purification device 510.

In step S510, the gas control unit 310 may determine whether it hasreceived, from the laser control unit 100, a signal for stopping partialgas replacement. The laser control unit 100 may send the signal forstopping partial gas replacement to the gas control unit 310 based onthe pressure P1 measured by the chamber pressure sensor 215 and thelike. In a case where the gas control unit 310 has received, from thelaser control unit 100, the signal for stopping partial gas replacement,the gas control unit 310 may terminate the operation of partial gasreplacement. In a case where the gas control unit 310 has not received,from the laser control unit 100, the signal for stopping partial gasreplacement, the gas control unit 310 may return to step S502.

In this manner, the laser apparatus 1000 according to the secondembodiment of the present disclosure makes it possible to purify a partof the gas in the chamber 210 and supply the purified gas to the chamber210. In this manner, the laser apparatus 1000 according to the secondembodiment of the present disclosure makes it possible to reduce theamount of a gas that is sent from the buffer gas supply source 3200 tothe chamber 210.

3.3 Laser Apparatus Including Gas Purification System According to ThirdEmbodiment of Present Disclosure

FIG. 9 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to a thirdembodiment of the present disclosure. The laser apparatus shown in FIG.9 may include the same configuration as the laser apparatus illustratedin FIG. 6. Components of the laser apparatus illustrated in FIG. 9 whichare identical to those of the laser apparatus illustrated in FIG. 6 aregiven the same reference signs, and as such, are omitted from thedescription below.

The laser apparatus according to the third embodiment of the presentdisclosure may include a plurality of excimer laser apparatuses such asa first excimer laser apparatus 1001 and a second excimer laserapparatus 1002.

One end of a circulation gas pipe of the gas purification system 500 maybe connected through a plurality of valves C-V1 of the plurality ofexcimer laser apparatuses to a plurality of pipes. The plurality ofpipes are connected to the plurality of chambers 210 of the plurality ofexcimer laser apparatuses, respectively, and to a plurality of exhaustdevices 330, respectively.

The other end of the circulation gas pipe of the gas purification system500 may be connected to a pipe connecting the buffer gas supply source3200 and the plurality of gas supply devices 320 of the plurality ofexcimer laser apparatuses. The pipe connecting the buffer gas supplysource 3200 and the plurality of gas supply devices 320 of the pluralityof excimer laser apparatuses may correspond to a common pipe in thepresent disclosure. A gas purified by the gas purification device 510may be supplied from the gas purification device 510 at completely orsubstantially the same pressure as the pressure of the regulator for thebuffer gas supply source 3200. This allows a single gas purificationdevice 510 to supply the purified gas to the plurality of excimer laserapparatuses.

The fluorine-containing gas supply source 3100 and the buffer gas supplysource 3200 may be connected to the plurality of gas supply devices 320of the plurality of excimer laser apparatuses.

The gas purification system 500 of the laser apparatus according to thethird embodiment of the present disclosure may further include anoximeter 600. The oximeter 600 may be one configured to measure theconcentration of oxygen in a gas flowing through the circulation gaspipe of the gas purification system 500. The oximeter 600 may beconfigured to send, to the gas purification control unit 520, datarepresenting the concentration of oxygen in the gas flowing through thecirculation gas pipe of the gas purification system 500.

In the laser apparatus according to the third embodiment of the presentdisclosure, a valve B-V2 may be provided to a pipe present between (i)the circulation gas pipe of the gas purification system 500 connected tothe plurality of gas supply devices 320 of the plurality of excimerlaser apparatuses and (ii) the regulator provided in the buffer gassupply source 3200.

The plurality of valves C-V1 of the plurality of excimer laserapparatuses may be controlled by the plurality of gas control units 310of the plurality of excimer laser apparatuses, respectively.

The gas purification control unit 520 may perform at least eithersending signals or receiving signals to or from the plurality of gascontrol units 310 through the laser control units 100 of the pluralityof excimer laser apparatuses.

The following describes an operation of exhaust for the circulation gaspipe of the gas purification device 510 in the excimer laser apparatus1000 according to the third embodiment of the present disclosure.

First, the gas purification control unit 520 may close the valve C-V3and may close the plurality of valves C-V1 of the plurality of excimerlaser apparatuses through the plurality of laser control units 100 andgas control units 310 of the plurality of excimer laser apparatuses.

Next, by bringing into operation an exhaust pump (not illustrated)connected to the circulation gas pipe of the gas purification device510, the circulation gas pipe of the gas purification device 510 may beexhausted until pressures measured by the first pressure sensor 514 andthe second pressure sensor 518 become pressures that are close to avacuum. In this manner, the circulation gas pipe of the gas purificationdevice may be brought into a state that is close to a vacuum.

FIG. 10 is a diagram illustrating an example of operation of the gaspurification control unit of the laser apparatus including the gaspurification system according to the third embodiment of the presentdisclosure.

In step S601, the gas purification control unit 520 may makepreparations for gas purification. In preparation for gas purification,the circulation gas pipe of the gas purification device 510 may befilled with a gas. In preparation for gas purification, the purificationcolumn 511 may be heated. In preparation for gas purification, thevalves C-V1 and the valve C-V3 may be closed.

In step S602, the gas purification control unit 520 may determinewhether it has received, from the laser control unit 100 of each excimerlaser apparatus through the gas control unit 310 of the correspondingexcimer laser apparatus, a signal for starting gas purification. Eachlaser control unit 100 may send the signal for starting gas purificationto the gas purification control unit 520 through the corresponding gascontrol unit 310 based on the predetermined number of shots of laseroscillation, the predetermined time intervals, and the like. In a casewhere the gas purification control unit 520 has received, from eachlaser control unit 100 through the corresponding gas control unit 310,the signal for starting gas purification, the gas purification controlunit 520 may proceed to step S603. In a case where the gas purificationcontrol unit 520 has not received, from each laser control unit 100through the corresponding gas control unit 310, the signal for startinggas purification, the gas purification control unit 520 may repeat stepS602.

In step S603, the gas purification control unit 520 may open the valveB-V2 and close the valve C-V3. That is, in a case where any of theplurality of gas control units 310 performs partial gas replacement, thesupply of the buffer gas from the buffer gas supply source 3200 to eachchamber 210 may be prepared.

In step S604, each gas control unit 310 may as needed control theopening and closing of the corresponding valve C-V1 and therebyintroduce the gas in the corresponding chamber 210 into the gaspurification device 510. The gas in each chamber 210 which is introducedinto the gas purification device 510 may be purified by the purificationcolumn 511 and the first filter 512 of the gas purification device 510.The gas thus purified may be supplied to the first tank 513 of the gaspurification device 510.

In step S605, the gas purification control unit 520 may control thebooster pump 515. The gas purification control unit 520 may receive apressure P2 of the gas in the first tank 513 as measured by the firstpressure sensor 514. The booster pump 515 may be controlled so that thepressure P2 of the gas in the first tank 513 may fall within apredetermined range of pressure. The booster pump 515 may be controlledso that the pressure P2 of the gas in the first tank 513 may satisfyP2min≦P2≦P2max. P2min may be the atmospheric pressure (1013 hPa). P2maxmay be a pressure (e.g., 1300 hPa) that is higher than the atmosphericpressure. The booster pump 515 may be configured to send the gascontained in the first tank 513 to the second tank 517. When thepressure P2 of the gas in the first tank 513 satisfies P2min≦P2, thebooster pump 515 may more efficiently send the gas contained in thefirst tank 513 to the second tank 517. When the pressure P2 of the gasin the first tank 513 satisfies P2≦P2max, the booster pump 515 may moreefficiently send a part of the gas in each chamber 210 to the first tank513 of the gas purification device 510.

In step S606, the gas purification control unit 520 may receive apressure P3 of the gas in the second tank 517 as measured by the secondpressure sensor 518.

In step S607, the gas purification control unit 520 may determinewhether the pressure P3 of the gas in the second tank 517 is equal to orhigher than a predetermined pressure P3reg. The predetermined pressureP3reg may be a pressure (e.g., 5000 hPa or higher and 5700 hPa or lower)indicated by a regulator provided in a pipe through which the buffer gasis supplied. In a case where the pressure P3 of the gas in the secondtank 517 is equal to or higher than the predetermined pressure P3reg,the gas purification control unit 520 may proceed to step S608. In acase where the pressure P3 of the gas in the second tank 517 is equal toor higher than the predetermined pressure P3reg, the gas in the secondtank 517 may be more efficiently sent to each chamber 210. In a casewhere the pressure P3 of the gas in the second tank 517 is not equal toor higher than the predetermined pressure P3reg, the gas purificationcontrol unit 520 may return to step S603.

In step S608, the gas purification control unit 520 may receive, fromthe oximeter 600, an oxygen concentration C in a gas flowing through thecirculation gas pipe of the gas purification device 510. The oxygenconcentration C may be measured by the oximeter 600 of the gaspurification control unit 520.

In step S609, the gas purification control unit 520 may determinewhether the oxygen concentration C in the gas flowing through thecirculation gas pipe of the gas purification device 510 is equal to orlower than a predetermined concentration Cmax. In a case where theoxygen concentration C in the gas flowing through the circulation gaspipe of the gas purification device 510 is equal to or lower than thepredetermined concentration Cmax, the gas purification control unit 520may proceed to step S610. In a case where the oxygen concentration C inthe gas flowing through the circulation gas pipe of the gas purificationdevice 510 is equal to or lower than the predetermined concentrationCmax, the purification column 511 may function normally. In a case wherethe oxygen concentration C in the gas flowing through the circulationgas pipe of the gas purification device 510 is not equal to or lowerthan the predetermined concentration Cmax, the gas purification controlunit 520 may proceed to step S611. In a case where the oxygenconcentration C in the gas flowing through the circulation gas pipe ofthe gas purification device 510 is not equal to or lower than thepredetermined concentration Cmax, the purification column 511 may notnecessarily function normally.

In step S610, the gas purification control unit 520 may close the valveB-V2 and open the valve C-V3. That is, in a case where any of theplurality of gas control units 310 performs partial gas replacement, thesupply of a gas purified by the gas purification device 510 from the gaspurification device 510 to each chamber 210 may be prepared. After stepS610, the gas purification control unit 520 may proceed to step S612.

In step S611, the gas purification control unit 520 may output, to eachlaser control unit 100, a signal for renewal or replacement of thepurification column 511 or a signal indicating that the purification ofa gas by the purification column 511 is difficult or impossible. In stepS611, renewal or replacement of the purification column 511 may beperformed.

In step S612, each gas control unit 310 may as needed control theopening and closing of the corresponding valve B-V1 and therebyintroduce the gas purified by the gas purification device 510 into thecorresponding chamber 210.

In step S613, the gas purification control unit 520 may determinewhether it has received, from each laser control unit 100 through thecorresponding gas control unit 310, a signal for stopping gaspurification. Each laser control unit 100 may send the signal forstopping gas purification to the gas purification control unit 520through the corresponding gas control unit 310 based on the pressure P1measured by a chamber pressure sensor (not illustrated) and the like. Ina case where the gas purification control unit 520 has received, fromeach laser control unit 100 through the corresponding gas control unit310, the signal for stopping gas purification, the gas purificationcontrol unit 520 may terminate the operation of gas purification. In acase where the gas purification control unit 520 has not received, fromeach laser control unit 100 through the corresponding gas control unit310, the signal for stopping gas purification, the gas purificationcontrol unit 520 may return to step S604.

FIG. 11 is a diagram illustrating an example of operation of each gascontrol unit of the laser apparatus including the gas purificationsystem according to the third embodiment of the present disclosure.

In step S701, each gas control unit 310 may make preparations forpartial gas replacement. In preparation for partial gas replacement, thevalve F2-V1 and valve B-V1 of each gas supply device 320, the valve Ex-Vof each exhaust device 330, and each valve C-V1 may all be closed. Inpreparation for partial gas replacement, the exhaust pump 332 of eachexhaust device 330 may be brought into operation.

In step S702, each gas control unit 310 may determine whether it hasreceived, from the corresponding laser control unit 100, a signal forstarting partial gas replacement. Each laser control unit 100 may sendthe signal for starting partial gas replacement to the corresponding gascontrol unit 310 based on a predetermined number of shots of laseroscillation, predetermined time intervals, and the like. In a case whereeach gas control unit 310 has received, from the corresponding lasercontrol unit 100, the signal for starting partial gas replacement, thegas control unit 310 may proceed to step S703. In a case where each gascontrol unit 310 has not received, from the corresponding laser controlunit 100, the signal for starting partial gas replacement, the gascontrol unit 310 may repeat step S702.

In step S703, each gas control unit 310 may receive an initial pressureP10 of the gas in the corresponding chamber 210 (i.e., a pressure of thegas in the corresponding chamber 210 before partial gas replacement)from the corresponding pressure sensor.

In step S704, each gas control unit 310 may calculate a target value P1b of the pressure of the gas in the corresponding chamber 210 aftersupplying the buffer gas or the purified gas to the correspondingchamber 210.

In step S705, each gas control unit 310 may receive the pressure P1 ofthe gas in the corresponding chamber 210 from the corresponding pressuresensor and may control the corresponding valve B-V1 so that the pressureP1 may become closer to the target value P1 b. At this point in time, ina case where the valve B-V2 is open and the valve C-V3 is closed, asdescribed in the aforementioned step S603, the buffer gas may besupplied from the buffer gas supply source 3200 to each chamber 210.Alternatively, in a case where the valve B-V2 is closed and the valveC-V3 is open, as described in the aforementioned step S610, the purifiedgas may be supplied from the gas purification device 510 to each chamber210. In this manner, each gas control unit 310 may cause the buffer gasor the purified gas to be supplied to the corresponding chamber 210.

In step S706, each gas control unit 310 may calculate a target valueΔP1F2 of a rise in pressure in the corresponding chamber 210 due tosupplying the fluorine-containing gas to the corresponding chamber 210.Each gas control unit 310 may calculate the target value ΔP1F2 of therise in pressure so that the concentration of a fluorine gas in the gasin the corresponding chamber 210 may become equal to a predeterminedconcentration CF2. For example, in a case where the fluorine-containinggas is a fluorine gas, the target value ΔP1F2 of the rise in pressuremay be calculated according to the formulae ΔP1 b=P1 b−P10 andΔP1F2=CF2×AP1 b/(1−CF2). In a case where the fluorine-containing gas isa mixed gas, the calculation may be performed further in considerationof a mixing ratio of fluorine.

In step S707, each gas control unit 310 may calculate a target valueP1F2 of the pressure of the gas in the corresponding chamber 210 aftersupplying the fluorine-containing gas to the corresponding chamber 210.The target value P1F2 of the pressure may be calculated according to theformula P1F2=P1 b+ΔP1F2.

In step S708, each gas control unit 310 may receive the pressure P1 ofthe gas in the corresponding chamber 210 from the corresponding pressuresensor and may control the corresponding valve F2-V1 so that thepressure P1 may become closer to the target value P1F2. In this manner,each gas control unit 310 may cause the fluorine-containing gas to besupplied to the corresponding chamber 210.

In step S709, each gas control unit 310 may receive the pressure P1 ofthe gas in the corresponding chamber 210 from the corresponding chamberpressure sensor 215 and may control the corresponding valve C-V1 so thatthe pressure P1 may become closer to the initial pressure P10. In thismanner, each gas control unit 310 may introduce a part of the gas in thecorresponding chamber 210 into the gas purification device 510.

In step S710, each gas control unit 310 may determine whether it hasreceived, from the corresponding laser control unit 100, a signal forstopping partial gas replacement. Each laser control unit 100 may sendthe signal for stopping partial gas replacement to the corresponding gascontrol unit 310 based on the pressure P1 measured by the correspondingpressure sensor and the like. In a case where each gas control unit 310has received, from the corresponding laser control unit 100, the signalfor stopping partial gas replacement, the gas control unit 310 mayterminate the operation of partial gas replacement. In a case where eachgas control unit 310 has not received, from the corresponding lasercontrol unit 100, the signal for stopping partial gas replacement, thegas control unit 310 may return to step S702.

3.4 Laser Apparatus Including Gas Purification System According toFourth Embodiment of Present Disclosure

FIG. 12 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to afourth embodiment of the present disclosure. The laser apparatus shownin FIG. 12 may include the same configuration as the laser apparatusillustrated in FIG. 9. Components of the laser apparatus illustrated inFIG. 12 which are identical to those of the laser apparatus illustratedin FIG. 9 are given the same reference signs, and as such, are omittedfrom the description below.

In the laser apparatus according to the fourth embodiment of the presentdisclosure, a gas supply source 3300 containing fluorine and a smallamount of xenon may be used instead of the fluorine-containing gassupply source 3100. The gas supply source 3300 may supply a gascontaining fluorine and a small amount of xenon to each chamber 210through the corresponding gas supply device 320. The gas containingfluorine and a small amount of xenon may be a mixed gas of fluorine,argon, neon, and xenon. The gas containing fluorine and a small amountof xenon may be a mixed gas of fluorine, krypton, neon, and xenon.

In the laser apparatus according to the fourth embodiment of the presentdisclosure, a buffer gas supply source 3400 containing a small amount ofxenon may be used instead of the buffer gas supply source 3200. Thebuffer gas supply source 3400 may supply a buffer gas containing a smallamount of xenon to each chamber 210 through the corresponding gas supplydevice 320. The buffer gas containing a small amount of xenon may be amixed gas of argon, neon, and xenon. The buffer gas containing a smallamount of xenon may be a mixed gas of krypton, neon, and xenon.

Use of gasses containing small amounts of xenon such as the gascontaining fluorine and a small amount of xenon and the buffer gascontaining a small amount of xenon may stabilize discharge of a gassupplied between the pair of discharge electrodes in each chamber 210.The concentration of xenon in a gas containing a small amount of xenonmay be approximately 10 ppm.

Meanwhile, xenon may produce XeF₂ by reacting with fluorine according tothe formula Xe+F₂→XeF₂. XeF₂ produced by the reaction between xenon andfluorine may be adsorbed to a metal surface to reduce the concentrationof xenon in the gas supplied to each chamber 210. Since the purificationcolumn 511, first filter 512, and second filter 516 of the gaspurification system 500 have metal surfaces with larger surface areas,XeF₂ may be adsorbed to the purification column 511, the first filter512, and the second filter 516. Such purification by the gaspurification system 500 of a part of the gas supplied to each chamber210 may reduce the concentration of xenon in the gas that is supplied toeach chamber 210. A reduction in the concentration of xenon in the gasthat is supplied to each chamber 210 may lead to a reduction in energyof initial pulse laser light during burst operation of the laserapparatus. The burst operation of the laser apparatus may be such thatlaser oscillation is executed at a predetermined repetition frequencyand the stoppage of laser oscillation is repeated at predetermined timeintervals.

In the laser apparatus according to the fourth embodiment of the presentdisclosure, a buffer gas supply source 3500 containing a large amount ofxenon may further be used. The buffer gas supply source 3500 may supplya buffer gas containing a large amount of xenon to each chamber 210through the corresponding gas supply device 320. The buffer gascontaining a large amount of xenon may be a mixed gas of argon, neon,and xenon. The buffer gas containing a large amount of xenon may be amixed gas of krypton, neon, and xenon.

The gas purification system 500 in the laser apparatus according to thefourth embodiment of the present disclosure may further include a valveXe-V1. The valve Xe-V1 may be provided to supply the buffer gascontaining a large amount of xenon from the buffer gas supply source3500 containing a large amount of xenon to a pipe through which apurified gas is supplied from the gas purification system 500 to eachgas supply device 320. The gas purification control unit 520 may send asignal to the valve Xe-V1, and the valve Xe-V1 may receive a signal fromthe gas purification control unit 520 and be controlled by the gaspurification control unit 520.

The gas purification device 510 in the laser apparatus according to thefourth embodiment of the present disclosure may further include a xenonconcentration meter 700. The xenon concentration meter 700 may beconfigured to measure the concentration of xenon in the gas purified bythe gas purification system 500. The xenon concentration meter 700 maybe a gas chromatograph mass spectrometer (GS-MS). The xenonconcentration meter 700 may be configured to send the concentration ofxenon in the purified gas to the gas purification control unit 520.

In the laser apparatus according to the fourth embodiment of the presentdisclosure, the gas purification control unit 520 may receive theconcentration of xenon in the purified gas from the xenon concentrationmeter 700 as measured by the xenon concentration meter 700. The gaspurification control unit 520 may control the opening and closing of thevalve Xe-V1, depending on the concentration of xenon in the purified gasas measured by the xenon concentration meter 700. For example, in a casewhere the concentration of xenon in the purified gas is lower than apredetermined concentration, the valve Xe-V1 may be opened to supply thebuffer gas containing a large amount of xenon so that the concentrationof xenon in the purified gas may become equal to the predeterminedconcentration. In this manner, a reduction in the concentration of xenonin the purified gas may be suppressed. Energy of pulse laser light thatis outputted from the laser apparatus according to the fourth embodimentof the present disclosure may be stabilized.

In the laser apparatus according to the fourth embodiment of the presentdisclosure, the concentration of xenon in the purified gas may bemeasured by the xenon concentration meter 700. However, changes inenergy of pulse light that is outputted from each excimer laserapparatus during burst operation and changes in charging voltage Vhvthat is supplied from each charger during burst operation may bemonitored. A reduction in the concentration of xenon in the purified gasmay be predicted from a relationship between the initial energy of pulselight that is outputted from each excimer laser apparatus during burstoperation and the charging voltage that is applied from each chargerduring burst operation. The gas containing xenon may be supplied to thepurified gas on the basis of the predicted reduction in xenonconcentration.

FIG. 13 is a diagram illustrating an example of operation of the gaspurification control unit of the laser apparatus including the gaspurification system according to the fourth embodiment of the presentdisclosure.

In step S801, the gas purification control unit 520 may makepreparations for gas purification. In preparation for gas purification,the circulation gas pipe of the gas purification device 510 may befilled with a gas. In preparation for gas purification, the purificationcolumn 511 may be heated. In preparation for gas purification, thevalves C-V1 and the valve C-V3 may be closed.

In step S802, the gas purification control unit 520 may determinewhether it has received, from the laser control unit 100 of each excimerlaser apparatus through the gas control unit 310 of that excimer laserapparatus, a signal for starting gas purification. Each laser controlunit 100 may send the signal for starting gas purification to the gaspurification control unit 520 through the corresponding gas control unit310 based on the predetermined number of shots of laser oscillation, thepredetermined time intervals, and the like. In a case where the gaspurification control unit 520 has received, from each laser control unit100 through the corresponding gas control unit 310, the signal forstarting gas purification, the gas purification control unit 520 mayproceed to step S803. In a case where the gas purification control unit520 has not received, from each laser control unit 100 through thecorresponding gas control unit 310, the signal for starting gaspurification, the gas purification control unit 520 may repeat stepS802.

In step S803, the gas purification control unit 520 may open the valveB-V2 and close the valve C-V3. In this manner, the gas purificationcontrol unit 520 may cause the buffer gas containing a small amount ofxenon to be supplied from the buffer gas supply source 3400 containing asmall amount of xenon to each chamber 210.

In step S804, each gas control unit 310 may as needed control theopening and closing of the corresponding valve C-V1 and therebyintroduce the gas in the corresponding chamber 210 into the gaspurification device 510. The gas in each chamber 210 which is introducedinto the gas purification device 510 may be purified by the purificationcolumn 511 and the first filter 512 of the gas purification device 510.The gas thus purified may be supplied to the first tank 513 of the gaspurification device 510.

In step S805, the gas purification control unit 520 may control thebooster pump 515. The gas purification control unit 520 may receive apressure P2 of the gas in the first tank 513 as measured by the firstpressure sensor 514. The booster pump 515 may be controlled so that thepressure P2 of the gas in the first tank 513 may fall within apredetermined range of pressure. The booster pump 515 may be controlledso that the pressure P2 of the gas in the first tank 513 may satisfyP2min≦P2≦P2max. P2min may be the atmospheric pressure (1013 hPa). P2maxmay be a pressure (e.g., 1300 hPa) that is higher than the atmosphericpressure. The booster pump 515 may be configured to send the gascontained in the first tank 513 to the second tank 517. When thepressure P2 of the gas in the first tank 513 satisfies P2min≦P2, thebooster pump 515 may more efficiently send the gas contained in thefirst tank 513 to the second tank 517. When the pressure P2 of the gasin the first tank 513 satisfies P2≦P2max, the booster pump 515 may moreefficiently send a part of the gas in each chamber 210 to the first tank513 of the gas purification device 510.

In step S806, the gas purification control unit 520 may receive apressure P3 of the gas in the second tank 517 as measured by the secondpressure sensor 518.

In step S807, the gas purification control unit 520 may determinewhether the pressure P3 of the gas in the second tank 517 is equal to orhigher than a predetermined pressure P3reg. The predetermined pressureP3reg may be a pressure (e.g., 5000 hPa or higher and 5700 hPa or lower)indicated by a regulator provided in a pipe through which the buffer gasis supplied. In a case where the pressure P3 of the gas in the secondtank 517 is equal to or higher than the predetermined pressure P3reg,the gas purification control unit 520 may proceed to step S808. In acase where the pressure P3 of the gas in the second tank 517 is equal toor higher than the predetermined pressure P3reg, the gas in the secondtank 517 may be more efficiently sent to each chamber 210. In a casewhere the pressure P3 of the gas in the second tank 517 is not equal toor higher than the predetermined pressure P3reg, the gas purificationcontrol unit 520 may return to step S803.

In step S808, the gas purification control unit 520 may receive, fromthe oximeter 600, an oxygen concentration C in a gas flowing through thecirculation gas pipe of the gas purification device 510. The oxygenconcentration C may be measured by the oximeter 600 of the gaspurification control unit 520.

In step S809, the gas purification control unit 520 may determinewhether the oxygen concentration C in the gas flowing through thecirculation gas pipe of the gas purification device 510 is equal to orlower than a predetermined concentration Cmax. In a case where theoxygen concentration C in the gas flowing through the circulation gaspipe of the gas purification device 510 is equal to or lower than thepredetermined concentration Cmax, the gas purification control unit 520may proceed to step S810. In a case where the oxygen concentration C inthe gas flowing through the circulation gas pipe of the gas purificationdevice 510 is equal to or lower than the predetermined concentrationCmax, the purification column 511 may function normally. In a case wherethe oxygen concentration C in the gas flowing through the circulationgas pipe of the gas purification device 510 is not equal to or lowerthan the predetermined concentration Cmax, the gas purification controlunit 520 may proceed to step S811. In a case where the oxygenconcentration C in the gas flowing through the circulation gas pipe ofthe gas purification device 510 is not equal to or lower than thepredetermined concentration Cmax, the purification column 511 may notnecessarily function normally.

In step S810, the gas purification control unit 520 may receive, fromthe xenon concentration meter 700, a xenon concentration Cxe in a gasflowing through the circulation gas pipe of the gas purification device510. The xenon concentration Cxe may be measured by the xenonconcentration meter 700 of the gas purification control unit 520. Thegas purification control unit 520 may proceed to step S812.

In step S811, the gas purification control unit 520 may output, to eachlaser control unit 100, a signal for renewal or replacement of thepurification column 511 or a signal indicating that the purification ofa gas by the purification column 511 is difficult or impossible. In stepS811, renewal or replacement of the purification column 511 may beperformed.

In step S812, the gas purification control unit 520 may control thevalve Xe-V1. The valve Xe-V1 may be controlled so that the xenonconcentration Cxe in the gas flowing through the circulation gas pipe ofthe gas purification device 510 may fall within a predetermined range.

In step S813, the gas purification control unit 520 may close the valveB-V2 and open the valve C-V3. In this manner, the gas purificationcontrol unit 520 may make preparations for the supply of the gaspurified by the gas purification device 510 from the gas purificationdevice 510 to each chamber 210.

In step S814, each gas control unit 310 may as needed control theopening and closing of the corresponding valve B-V1 and therebyintroduce the gas purified by the gas purification device 510 into thecorresponding chamber 210.

In step S815, the gas purification control unit 520 may determinewhether it has received, from each laser control unit 100 through thecorresponding gas control unit 310, a signal for stopping gaspurification. Each laser control unit 100 may send the signal forstopping gas purification to the gas purification control unit 520through the corresponding gas control unit 310 based on the pressure P1measured by a chamber pressure sensor (not illustrated) and the like. Ina case where the gas purification control unit 520 has received, fromeach laser control unit 100 through the corresponding gas control unit310, the signal for stopping gas purification, the gas purificationcontrol unit 520 may terminate the operation of gas purification. In acase where the gas purification control unit 520 has not received, fromeach laser control unit 100 through the corresponding gas control unit310, the signal for stopping gas purification, the gas purificationcontrol unit 520 may return to step 3804.

3.5 Laser Apparatus Including Gas Purification System According to FifthEmbodiment of Present Disclosure

FIG. 14 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to a fifthembodiment of the present disclosure. The laser apparatus shown in FIG.14 may include the same configuration as the laser apparatus illustratedin FIG. 9. Components of the laser apparatus illustrated in FIG. 14which are identical to those of the laser apparatus illustrated in FIG.9 are given the same reference signs, and as such, are omitted from thedescription below.

In the laser apparatus according to the fifth embodiment of the presentdisclosure, not the gas purification device 510 but each excimer laserapparatus may be provided with a purification column 511 and a firstfilter 512. Providing each excimer laser apparatus with the purificationcolumn 511 and the first filter 512 allows a purified gas to flowthrough a pipe between that excimer laser apparatus and the gaspurification device 510.

3.6 Laser Apparatus Including Gas Purification System According to SixthEmbodiment of Present Disclosure

FIG. 15 is a diagram illustrating an example of a configuration of alaser apparatus including a gas purification system according to a sixthembodiment of the present disclosure. The laser apparatus shown in FIG.15 may include the same configuration as the laser apparatus illustratedin FIG. 12. Components of the laser apparatus illustrated in FIG. 15which are identical to those of the laser apparatus illustrated in FIG.12 are given the same reference signs, and as such, are omitted from thedescription below.

In the laser apparatus according to the sixth embodiment of the presentdisclosure, each gas supply device 320 may include a buffer gas cylinder350 containing a large amount of xenon instead of the buffer gas supplysource containing a large amount of xenon. The buffer gas cylinder 350may supply a buffer gas containing a large amount of xenon to thecorresponding chamber 210. The buffer gas cylinder 350 may be small insize, e.g., a cylinder of approximately 1 liter.

In the laser apparatus according to the sixth embodiment of the presentdisclosure, each gas supply device 320 may include a valve Xe-V1 insteadof the valve Xe-V1 of the gas purification system 500. The valve Xe-V1of each gas supply device 320 may be provided in a pipe connecting thecorresponding buffer gas cylinder 350 and the corresponding chamber 210.The valve Xe-V1 may be controlled by the corresponding gas control unit310.

FIGS. 16A to 16D are each a diagram for explaining a principle ofestimation of a xenon concentration on the basis of changes in energy Eof pulse light during burst operation in the laser apparatus includingthe gas purification system according to the sixth embodiment of thepresent disclosure.

FIG. 16A shows changes in pulse energy E in the early phase of burstoperation in a case where the xenon concentration is a concentration Ctthat is close to an optimum value and the charging voltage V isconstant. In a case where the xenon concentration is close to theoptimum value, the stability of the pulse energy E may be high and thedifference between the maximum value Emax of the pulse energy E and theminimum value Emin of the pulse energy E may be small.

FIG. 16B shows changes in pulse energy E in the early phase of burstoperation in a case where the xenon concentration is a concentration C1that is lower than the optimum value and the charging voltage V isconstant. When the xenon concentration is lower, the stability of thepulse energy E may be lower and the difference between the maximum valueEmax of the pulse energy E and the minimum value Emin of the pulseenergy E may be larger.

FIG. 16C shows changes in pulse energy E in the early phase of burstoperation in a case where the xenon concentration is a concentration C2that is even lower than the concentration C1 and the charging voltage Vis constant. When the xenon concentration is even lower, the stabilityof the pulse energy E may be even lower and the difference between themaximum value Emax of the pulse energy E and the minimum value Emin ofthe pulse energy E may be even larger.

In this manner, the stability of the pulse energy E in the early phaseof burst operation in a case where the charging voltage V is constantmay be correlated with the xenon concentration.

FIG. 16D shows a relationship between the stability of the pulse energyE in the early phase of burst operation and the xenon concentration Cxein a case where the charging voltage V is constant. The stability of thepulse energy may be indicated by a ratio Er of the minimum value Emin tothe maximum value Emax. The ratio Er is represented by the followingformula:

Er=Emin/Emax

As shown in FIG. 16D, the xenon concentration Cxe may be expressed as afunction f(Er) of the ratio Er, and this function may be stored. Use ofthe relationship between the ratio Er and the xenon concentration Cxemakes it possible to estimate the xenon concentration Cxe from the ratioEr without using a xenon concentration meter.

FIGS. 17A to 17D are each a diagram for explaining a principle ofestimation of a xenon concentration on the basis of changes in chargingvoltage V by a charger during burst operation in the laser apparatusincluding the gas purification system according to the sixth embodimentof the present disclosure.

FIG. 17A shows changes in charging voltage V in the early phase of burstoperation in a case where the xenon concentration is a concentration Ctthat is close to an optimum value and the pulse energy E is constant. Ina case where the xenon concentration is close to the optimum value, thestability of the charging voltage V may be high and the differencebetween the maximum value Vmax of the charging voltage V and the minimumvalue Vmin of the charging voltage V may be small.

FIG. 17B shows changes in charging voltage V in the early phase of burstoperation in a case where the xenon concentration is a concentration C1that is lower than the optimum value and the pulse energy E is constant.When the xenon concentration is lower, the stability of the chargingvoltage V may be lower and the difference between the maximum value Vmaxof the charging voltage V and the minimum value Vmin of the chargingvoltage V may be larger.

FIG. 17C shows changes in charging voltage V in the early phase of burstoperation in a case where the xenon concentration is a concentration C2that is even lower than the concentration C1 and the pulse energy E isconstant. When the xenon concentration is even lower, the stability ofthe charging voltage V may be even lower and the difference between themaximum value Vmax of the charging voltage V and the minimum value Vminof the charging voltage V may be even larger.

In this manner, the stability of the charging voltage V in the earlyphase of burst operation in a case where the pulse energy E is constantmay be correlated with the xenon concentration.

FIG. 17D shows a relationship between the stability of the chargingvoltage V in the early phase of burst operation and the xenonconcentration Cxe in a case where the pulse energy E is constant. Thestability of the charging voltage V may be indicated by a ratio Vr ofthe minimum value Vmin to the maximum value Vmax. The ratio Vr isrepresented by the following formula:

Vr=Vmin/Vmax

As shown in FIG. 17D, the xenon concentration Cxe may be expressed as afunction g(Vr) of the ratio Vr, and this function may be stored. Use ofthe relationship between the ratio Vr and the xenon concentration Cxemakes it possible to estimate the xenon concentration Cxe from the ratioVr without using a xenon concentration meter.

FIG. 18 is a diagram illustrating an example of operation of a lasercontrol unit of the laser apparatus including the gas purificationsystem according to the sixth embodiment of the present disclosure. Thelaser control unit 100 may estimate the xenon concentration Cxe throughthe following process. It should be noted the same process as that shownin FIG. 18 may be performed in the fourth embodiment.

In step S910, the laser control unit 100 may determine whether to checkthe xenon concentration. For example, the laser control unit 100 maydetermine to check the xenon concentration when a predetermined periodof time has elapsed since it checked the xenon concentration last. In acase where the laser control unit 100 checks the xenon concentration,the laser control unit 100 may proceed to step S920. In a case where thelaser control unit 100 does not check the xenon concentration, the lasercontrol unit 100 may repeat step S910.

In step S920, the laser control unit 100 may output a signalrepresenting exposure NG to the exposure device controller 2100 of theexposure device 2000. This may enable operation in such a burst patternas to show the effect of a reduction in xenon concentration.

In step S930, the laser control unit 100 may estimate the xenonconcentration Cxe by measuring burst characteristics. This process willbe described in detail later with reference to FIGS. 20 and 21.

In step S950, the laser control unit 100 may determine whether the xenonconcentration Cxe estimated in step S930 is equal to or lower than apredetermined threshold Cxet. In a case where the xenon concentrationCxe is not equal to or less than a predetermined threshold Cxet, thelaser control unit 100 may proceed to step S960 in order to resume theexposure process. In a case where the xenon concentration Cxe is equalto or lower than the predetermined threshold Cxet, the laser controlunit 100 may proceed to step S970 in order to cause the gas control unit310 to execute xenon injection.

In step S960, the laser control unit 100 may output a signalrepresenting exposure OK to the exposure device controller 2100 of theexposure device 2000. After step S960, the laser control unit 100 mayreturn to step S910.

In step S970, the laser control unit 100 may send data representing thexenon concentration Cxe to the gas control unit 310. This may enable thegas control unit 310 to execute a process for xenon injection.

In step S980, the laser control unit 100 may determine whether it hasreceived a xenon injection signal from the gas control unit 310. In acase where it has not received a xenon injection signal, the lasercontrol unit 100 may repeat step S980. In a case where it has received axenon injection signal, the laser control unit 100 may return to S930 inorder to newly estimate a xenon concentration.

FIG. 19 is a diagram illustrating an example of operation of a gascontrol unit of the laser apparatus including the gas purificationsystem according to the sixth embodiment of the present disclosure. Thegas control unit 310 may control the valve Xe-V1 through the followingprocess. It should be noted the same process as that shown in FIG. 19may be performed by the gas purification control unit in the fourthembodiment.

In step S991, the gas control unit 310 may determine whether it hasreceived data representing the xenon concentration Cxe from the lasercontrol unit 100. The data representing the xenon concentration Cxe maybe data that is sent from the laser control unit 100 in step S970described with reference to FIG. 18. In a case where the gas controlunit 310 has not received data representing the xenon concentration Cxe,the gas control unit 310 may repeat step S991. In a case where the gascontrol unit 310 has received data representing the xenon concentrationCxe, the gas control unit 310 may proceed to step S992.

In step S992, the gas control unit 310 may calculate the difference ΔCxebetween the xenon concentration Cxe and the target concentration Ctaccording to the following formula:

ΔCxe=Cxe−Ct

The target concentration Ct may be a concentration that is close to theoptimum value described with reference to FIG. 16A or 17A. The targetconcentration Ct may be a concentration that is higher than thethreshold Cxet described with reference to FIG. 18.

In step S993, the gas control unit 310 may control the valve Xe-V1 sothat the difference ΔCxe may become closer to 0. By controlling thevalve Xe-V1, a small amount of a xenon gas may be supplied into thechamber.

In step S994, the gas control unit 310 may wait for a predeterminedperiod of time. This predetermined period of time may be a period oftime assumed as a period of time it takes to show the effect of xenoninjection.

In step S995, the gas control unit 310 may send a xenon injection signalto the laser control unit 100. The xenon injection signal may be asignal that the laser control unit 100 receives in step S980 describedwith reference to FIG. 18. After step S995, the gas control unit 310 mayreturn to step S991.

FIGS. 20 and 21 are each a diagram illustrating an example of operationin which the laser control unit of the laser apparatus including the gaspurification system according to the sixth embodiment of the presentdisclosure estimates the xenon concentration Cxe.

FIG. 20 shows a first example of an operation for estimating the xenonconcentration Cxe on the basis of the stability of the pulse energy E.The operation shown in FIG. 20 may be performed by the laser controlunit 100 as a subroutine of step S930 shown in FIG. 18.

In step S931, the laser control unit 100 may set the charging voltage Vby the charger at a constant value.

In step S932, the laser control unit 100 may start burst operation in apredetermined pattern. The burst operation may include repetition of atrigger pattern including oscillation at a repetition frequency of 6 kHzfor 1 second and then a pause for 1 second, for example, so as to easilyshow the effect of a reduction in xenon concentration.

In step S933, the laser control unit 100 may obtain data representingthe pulse energy E during burst operation from the power monitor 220.

In step S934, the laser control unit 100 may calculate the ratio Er ofthe minimum value Emin of the pulse energy E to the maximum value Emaxof the pulse energy E according to the following formula:

Er=Emin/Emax

In step S935, the laser control unit 100 may calculate the xenon gasconcentration Cxe on the basis of the ratio Er of the minimum value Eminof the pulse energy E to the maximum value Emax of the pulse energy E.

After step S935, the laser control unit 100 may proceed to step S950described with reference to FIG. 18.

FIG. 21 shows a second example of an operation for estimating the xenonconcentration Cxe on the basis of the stability of the charging voltageV. The operation shown in FIG. 21 may be performed by the laser controlunit 100 as a subroutine of step S930 shown in FIG. 18.

In step S936, the laser control unit 100 may set a target value of thepulse energy E at a constant value.

In step S937, the laser control unit 100 may start burst operation in apredetermined pattern. The burst operation may include repetition of atrigger pattern including oscillation at a repetition frequency of 6 kHzfor 1 second and then a pause for 1 second, for example, so as to easilyshow the effect of a reduction in xenon concentration.

In step S938, the laser control unit 100 may obtain data representingthe charging voltage V during burst operation.

In step S939, the laser control unit 100 may calculate the ratio Vr ofthe minimum value Vmin of the charging voltage V to the maximum valueVmax of the charging voltage V according to the following formula:

Vr=Vmin/Vmax

In step S940, the laser control unit 100 may calculate the xenon gasconcentration Cxe on the basis of the ratio Vr of the minimum value Vminof the charging voltage V to the maximum value Vmax of the chargingvoltage V.

After step S940, the laser control unit 100 may proceed to step S950described with reference to FIG. 18.

In a case where, during the burst operation shown in FIGS. 17A, 17B, and21, the charging voltage V is controlled so that an approximation to apredetermined pulse energy may be made and the xenon concentration isestimated on the basis of a change in charging voltage V at that time,the xenon concentration may be estimated during actual exposure. Thiseliminates the need to perform the process in steps S920 and S960 ofFIG. 18.

Further, as shown in the graphs of FIGS. 16D and 17D, as the xenonconcentration increases to go beyond the target concentration Ct, the Erand Vr values may reach the respective maximum values and then the Erand Vr values may decrease. In this case, the gas control unit mayexhaust a part of the laser gas and inject a new laser gas so that thexenon concentration may become lower.

4. Controller According to Embodiment of Present Disclosure

FIG. 22 is a diagram illustrating an example of a controller accordingto an embodiment of the present disclosure.

Each of the controllers in the above-described embodiments may beconstituted by a general-purpose control device such as a computer or aprogrammable controller. For example, the controller may be constitutedas described below.

(Configuration)

The controller may include a processing unit 4000, and a storage memory4005, a user interface 4010, a parallel input/output (I/O) controller4020, a serial I/O controller 4030, and an analog-to-digital (A/D) anddigital-to-analog (D/A) converter 4040 that are connected to theprocessing unit 4000. The processing unit 4000 may include a centralprocessing unit (CPU) 4001, and a memory 4002, a timer 4003, and agraphics processing unit (GPU) 4004 that are connected to the CPU 4001.

(Operation)

The processing unit 4000 may read out programs stored in the storagememory 4005. The processing unit 4000 may execute read-out programs,read out data from the storage memory 4005 in accordance with theexecution of the programs, or store data in the storage memory 4005.

The parallel I/O controller 4020 may be connected to devicescommunicable through parallel I/O ports. The parallel I/O controller4020 may control communication using digital signals through parallelI/O ports that is performed in the process where the processing unit4000 executes programs.

The serial I/O controller 4030 may be connected to devices communicablethrough serial I/O ports. The serial I/O controller 4030 may controlcommunication using digital signals through serial I/O ports that isperformed in the process where the processing unit 4000 executesprograms.

The A/D and D/A converter 4040 may be connected to devices communicablethrough analog ports. The A/D and D/A converter 4040 may controlcommunication using analog signals through analog ports that isperformed in the process where the processing unit 4000 executesprograms.

The user interface 4010 may be configured to display progress of programexecution by the processing unit 4000 to an operator or to receiveinstructions by the operator to the processing unit 4000 to stopexecution of the programs or to execute interruption processing.

The CPU 4001 of the processing unit 4000 may perform arithmeticprocessing of programs. In the process where the CPU 4001 executesprograms, the memory 4002 may temporally store programs or temporallystore data in the arithmetic process. The timer 4003 may measure time orelapsed time to output the time or the elapsed time to the CPU 4001 inaccordance with the execution of the programs. When image data is inputto the processing unit 4000, the GPU 4004 may process the image data inaccordance with the execution of the programs and output the results tothe CPU 4001.

(Connected Devices)

The devices communicable through parallel I/O ports, which are connectedto the parallel I/O controller 4020, may be parallel I/O devices 5010such as the emission trigger Tr, the charger, the control valves, andthe like.

The devices communicable through serial I/O ports, which are connectedto the serial I/O controller 4030, may be serial I/O devices 5020 suchas the laser control unit, the gas control unit, and the gaspurification control unit.

The devices communicable through analog ports, which are connected tothe A/D and D/A converter 4040, may be analog I/O devices 5030 such asthe optical sensor 223 and a pressure sensor.

The aforementioned descriptions are intended to be taken only asexamples, and are not to be seen as limiting in any way. Accordingly, itwill be clear to those skilled in the art that variations on theembodiments of the present disclosure can be made without departing fromthe scope of the appended claims.

The terms used in the present specification and in the entirety of thescope of the appended claims are to be interpreted as not beinglimiting. For example, wording such as “includes” or “is included”should be interpreted as not being limited to the item that is describedas being included. Furthermore, “has” should be interpreted as not beinglimited to the item that is described as being had. Furthermore, themodifier “a” or “an” as used in the present specification and the scopeof the appended claims should be interpreted as meaning “at least one”or “one or more”.

REFERENCE SIGNS LIST

-   -   100 Laser control unit    -   200 Laser oscillation system    -   210 Chamber    -   211 a, 211 b Discharge electrode    -   212 a, 212 b Window    -   213 Pulse power module    -   214 Switch    -   215 Chamber pressure sensor    -   220 Power monitor    -   221 Beam splitter    -   222 Collector lens    -   223 Optical sensor    -   230 Charger    -   240 Output coupling mirror    -   250 Line narrow module    -   251 Prism    -   252 Grating    -   300 Gas control system    -   310 Gas control unit    -   320 Gas supply device    -   330 Exhaust device    -   331 Fluorine trap    -   332 Exhaust pump    -   400 Gas purification system    -   410 Gas purification device    -   411 Purification column    -   412 Filter    -   413 Circulation pump    -   414 Mass flow controller    -   420 Gas purification control unit    -   500 Gas purification system    -   510 Gas purification device    -   511 Purification column    -   512 First filter    -   513 First tank    -   514 First pressure sensor    -   515 Booster pump    -   516 Second filter    -   517 Second tank    -   518 Second pressure sensor    -   519 Purifier    -   520 Gas purification control unit    -   600 Oximeter    -   700 Xenon concentration meter    -   1000 Excimer laser apparatus    -   1001 First excimer laser apparatus    -   1002 Second excimer laser apparatus    -   2000 Exposure device    -   2100 Exposure device controller    -   3100 Fluorine-containing gas supply source    -   3200 Buffer gas supply source    -   3300 Gas supply source containing fluorine and a small amount of        xenon    -   3400 Buffer gas supply source containing a small amount of xenon    -   3500 Buffer gas supply source containing a large amount of xenon    -   4000 Processing unit    -   4001 CPU    -   4002 Memory    -   4003 Timer    -   4004 GPU    -   4005 Storage memory    -   4010 User interface    -   4020 Parallel I/O controller    -   4030 Serial I/O controller    -   4040 A/D or D/A converter    -   5010 Parallel I/O device    -   5020 Serial I/O device    -   5030 Analog I/O device

1. A gas laser apparatus comprising: a laser chamber connected through afirst control valve to a first laser gas supply source that supplies afirst laser gas containing a halogen gas and connected through a secondcontrol valve to a second laser gas supply source that supplies a secondlaser gas having a lower halogen gas concentration than the first lasergas; a purification column that removes at least a part of the halogengas and a halogen compound from at least a part of a gas exhausted fromthe laser chamber; a booster pump, connected through a third controlvalve to the laser chamber, which raises a pressure of a gas havingpassed through the purification column to a gas pressure that is higherthan an operating gas pressure of the laser chamber; and a controllerthat calculates, on a basis of a first amount of a gas supplied from thebooster pump through the third control valve to the laser chamber, asecond amount of the first laser gas that is to be supplied to the laserchamber and controls the first control valve on a basis of a result ofthe calculation of the second amount.
 2. A gas laser apparatuscomprising: a laser chamber connected through a first control valve to afirst laser gas supply source that supplies a first laser gas containinga halogen gas and connected through a second control valve to a secondlaser gas supply source that supplies a second laser gas having a lowerhalogen gas concentration than the first laser gas; a purificationcolumn that removes at least a part of the halogen gas and a halogencompound from at least a part of a gas exhausted from the laser chamber;a booster pump, connected through a third control valve to the laserchamber, which raises a pressure of a gas having passed through thepurification column to a gas pressure that is higher than an operatinggas pressure of the laser chamber; a first tank disposed between thepurification column and the booster pump; a first pressure sensor thatmeasures a first pressure inside the first tank; a second tank disposedbetween the booster pump and the third control valve; a second pressuresensor that measures a second pressure inside the second tank; and acontroller that controls the booster pump on a basis of the firstpressure and controls the third control valve on a basis of the secondpressure.
 3. The gas laser apparatus according to claim 2, wherein thecontroller controls the booster pump so that the first pressure is equalto or higher than a first predetermined value and equal to or lower thana second predetermined value and permits the third control valve to openif the second pressure is equal to or higher than a third predeterminedvalue.
 4. A gas laser apparatus comprising: a laser chamber connectedthrough a first control valve to a first laser gas supply source thatsupplies a first laser gas containing a halogen gas and connectedthrough a second control valve to a second laser gas supply source thatsupplies a second laser gas having a lower halogen gas concentrationthan the first laser gas; a fourth control valve disposed between thesecond laser gas supply source and the second control valve; apurification column that removes at least a part of the halogen gas anda halogen compound from at least a part of a gas exhausted from thelaser chamber; a booster pump, connected through a third control valveto a pipe between the fourth control valve and the second control valve,which raises a pressure of a gas having passed through the purificationcolumn to a gas pressure that is higher than an operating gas pressureof the laser chamber; and a controller that selectively executes a firstcontrol mode in which the third control valve is closed and the fourthcontrol valve is opened and a second control mode in which the fourthcontrol valve is closed and the third control valve is opened.
 5. Thegas laser apparatus according to claim 4, further comprising: a firsttank disposed between the purification column and the booster pump; afirst pressure sensor that measures a first pressure inside the firsttank; a second tank disposed between the booster pump and the thirdcontrol valve; and a second pressure sensor that measures a secondpressure inside the second tank, wherein the controller controls thebooster pump on a basis of the first pressure and controls the thirdcontrol valve on a basis of the second pressure.
 6. The gas laserapparatus according to claim 5, wherein the controller controls thebooster pump so that the first pressure is equal to or higher than afirst predetermined value and equal to or lower than a secondpredetermined value and permits the third control valve to open if thesecond pressure is equal to or higher than a third predetermined value.7. The gas laser apparatus according to claim 1, wherein the first lasergas contains a fluorine gas, an argon gas, a neon gas, and a xenon gas,and the second laser gas contains an argon gas, a neon gas, and a xenongas.
 8. The gas laser apparatus according to claim 7, wherein the laserchamber is connected through a fifth control valve to a third laser gassupply source that supplies a third laser gas having a higher xenon gasconcentration than the second laser gas.
 9. The gas laser apparatusaccording to claim 8, further comprising a xenon concentration meterthat measures a xenon gas concentration of the gas having passed throughthe purification column, wherein the controller controls the fifthcontrol valve on a basis of the xenon gas concentration.
 10. The gaslaser apparatus according to claim 8, further comprising an operatingcharacteristic measuring instrument that measures an operatingcharacteristic of laser light that is outputted from the laser chamber,wherein the controller controls the fifth control valve on a basis ofthe operating characteristic.
 11. A gas laser apparatus comprising: afirst laser chamber connected through a first control valve to a firstlaser gas supply source that supplies a first laser gas containing ahalogen gas and connected through a second control valve to a secondlaser gas supply source that supplies a second laser gas having a lowerhalogen gas concentration than the first laser gas; a second laserchamber connected through a sixth control valve to the first laser gassupply source and connected through a seventh control valve to thesecond laser gas supply source; a common pipe connected to the secondlaser gas supply source and divided into a first branch pipe in whichthe second control valve is disposed and a second branch pipe in whichthe seventh control valve is disposed; a fourth control valve disposedin the common pipe; a purification column that removes at least a partof the halogen gas and a halogen compound from at least a part of a gasexhausted from the first laser chamber and at least a part of a gasexhausted from the second laser chamber; and a booster pump, connectedthrough a third control valve to the common pipe between the fourthcontrol valve and a place where the common pipe is divided into thefirst and second branch pipes, which raises a pressure of a gas havingpassed through the purification column to a gas pressure that is higherthan an operating gas pressure of the first laser chamber and anoperating gas pressure of the second laser chamber.